Exactly the same thing happened this morning.

Ok, i gave another try to the cam support (only recieving, i dont have a webcam) for yahoo's protocol. This time i recieved immages but after some seconds the immage stopped. The normal IM functionality keept functioning for some other seconds then i got disconnected from yahoo. Then i restarted kopete.
I saw no code changes from my first try till now, so seems the crash is not that easy to reproduce. But this time i started kopete from console so i have the debugging messages of the session described. For obvious reasons i changed the accounts and IM messages in the debug log, substituted them with xxx or such.
Except some messages that were not personal, ex. when i asked the other to start the cam and when the immage stopped.
Hope it helps.
I'll put the log as attachment.

Created attachment 12764 [details]
debug log of the cam session on yahoo

You can see all the activity, before i begin to recieve cam immages, when the
immage stops (read the IM messages i left in the debug) till after i get
disconnected from yahoo.

Hi,
Are you sure that your libyahoo2 was recompiled (was changed on Aug 29)?
The symptoms are the same as the random disconnects i got when yahoo introduced their new client version and decided to doom YMSG10 clients.

Yes, the checkout was done some days before the crash. 

*** Bug 117274 has been marked as a duplicate of this bug. ***

SVN commit 485011 by duffeck:

Fix Webcam disconnects/crashes.
BUG:113439


 M  +51 -24    kyahoo.cpp  
 M  +4 -4      kyahoo.h  


--- branches/KDE/3.5/kdenetwork/kopete/protocols/yahoo/kyahoo.cpp #485010:485011
@@ -88,27 +88,26 @@
 {
 }
 
-void YahooConnectionManager::addConnection( KStreamSocket* socket )
+void YahooConnectionManager::addConnection( QPair< KStreamSocket*, void *> *connection )
 {
-	kdDebug(14181) << k_funcinfo << "Adding socket with fd " << socket->socketDevice()->socket() << endl;
+	kdDebug(14181) << k_funcinfo << "Adding socket with fd " << connection->first->socketDevice()->socket() << endl;
 	
-	m_connectionList.append( socket );
+	m_connectionList.append( connection );
 }
 
-KStreamSocket* YahooConnectionManager::connectionForFD( int fd )
+QPair< KStreamSocket*, void *> *YahooConnectionManager::connectionForFD( int fd )
 {
 	//kdDebug(14181) << k_funcinfo << "Looking for socket with fd " << fd << endl;
-	QValueList<KStreamSocket*>::const_iterator it, ycEnd = m_connectionList.constEnd();
+	QValueList< QPair< KStreamSocket*, void *> *>::const_iterator it, ycEnd = m_connectionList.constEnd();
 	KSocketDevice *dev;
 	
 	for ( it = m_connectionList.begin(); it != ycEnd; ++it )
 	{
-		dev = ( *it )->socketDevice();
+		dev = ( *it )->first->socketDevice();
 		if ( dev->socket() == fd )
 		{
 			//kdDebug(14181) << k_funcinfo << "Found socket" << endl;
-			KStreamSocket* socket = ( *it );
-			return socket;
+			return *it;
 		}
 	}
 	
@@ -117,11 +116,11 @@
 
 void YahooConnectionManager::remove( KStreamSocket* socket )
 {
-	QValueList<KStreamSocket*>::iterator it, ycEnd = m_connectionList.end();
+	QValueList< QPair< KStreamSocket*, void *> *>::iterator it, ycEnd = m_connectionList.end();
 	
 	for ( it = m_connectionList.begin(); it != ycEnd; it++ )
 	{
-		if ( ( *it ) == socket )
+		if ( ( *it )->first == socket )
 		{
 			socket->reset();
 			m_connectionList.remove( it );
@@ -133,11 +132,11 @@
 
 void YahooConnectionManager::reset()
 {
-	QValueList<KStreamSocket*>::iterator it, ycEnd = m_connectionList.end();
+	QValueList< QPair< KStreamSocket*, void *> *>::iterator it, ycEnd = m_connectionList.end();
 	
 	for ( it = m_connectionList.begin(); it != ycEnd; it++ )
 	{
-		KStreamSocket *socket = ( *it );
+		KStreamSocket *socket = ( *it )->first;
 		socket->reset();
 		it = m_connectionList.remove( it );
 		delete socket;
@@ -1072,7 +1071,11 @@
 
 void YahooSession::slotTransmitFile( int fd, YahooUploadData *uploadData )
 {
-	KStreamSocket* socket = m_connManager.connectionForFD( fd );
+	QPair< KStreamSocket*, void *> *connection =  m_connManager.connectionForFD( fd );
+	if( !connection )
+		return;
+		
+	KStreamSocket* socket = connection->first;
 	if( !socket )
 		return;
 	
@@ -1160,9 +1163,15 @@
 		KMessageBox::error(Kopete::UI::Global::mainWidget(), i18n( "An error occurred when trying to download the file." ), i18n("Error") );
 		return;
 	}
+	QPair< KStreamSocket*, void *> *connection =  m_connManager.connectionForFD( fd );
+	if( !connection )
+	{
+		kdDebug(14181) << k_funcinfo << "No connection found for fd." << endl;
+		return;
+	}
 	
-	KStreamSocket* socket = m_connManager.connectionForFD( fd );
-	if ( !socket )
+	KStreamSocket* socket = connection->first;
+	if( !socket )
 	{
 		kdDebug(14181) << k_funcinfo << "No existing socket for connection found. We're screwed" << endl;
 		return;
@@ -1423,21 +1432,23 @@
 {
 	//kdDebug(14181) << k_funcinfo << " " << m_connId << " Socket: " << fd << endl;
 
-	m_data = data;
 	if ( fd == -1 )
 	{
 		kdDebug(14181) << k_funcinfo << "why is fd -1?" << endl;
 		return -1;
 	}
 	
-	KStreamSocket* socket = m_connManager.connectionForFD( fd );
-	if ( !socket )
+	QPair< KStreamSocket*, void *> *connection = m_connManager.connectionForFD( fd );
+	if ( !connection )
 	{
 		kdDebug(14181) << k_funcinfo << "No existing socket for connection found. We're screwed"
 			<< endl;
 		return -1;
 	}
 	
+	KStreamSocket *socket = connection->first;
+	connection->second = data;
+	
 	/* This works ONLY IF (YAHOO_INPUT_READ==1 && YAHOO_INPUT_WRITE==2) */
 	int tag = 0;
 	if ( cond == YAHOO_INPUT_READ )
@@ -1468,13 +1479,14 @@
 	if ( tag == 0 )
 		return;
 
-	KStreamSocket* socket = m_connManager.connectionForFD( (tag-1)/2 );
-	if ( !socket )
+	QPair< KStreamSocket*, void *> *connection = m_connManager.connectionForFD( (tag-1)/2 );
+	if ( !connection )
 	{
 		kdDebug(14181) << k_funcinfo << "No existing socket for connection found. We're screwed"
 			<< endl;
 		return;
 	}
+	KStreamSocket *socket = connection->first;
 	/* This works ONLY IF (YAHOO_INPUT_READ==1 && YAHOO_INPUT_WRITE==2) */
 	if( tag % 2 == YAHOO_INPUT_READ ) {
 		//kdDebug(14181) << k_funcinfo << " read off" << endl;
@@ -1522,7 +1534,8 @@
 {
 	KStreamSocket* socket = const_cast<KStreamSocket*>( dynamic_cast<const KStreamSocket*>( sender() ) );
 	kdDebug(14181) << k_funcinfo << " Connected! fd "<< socket->socketDevice()->socket() << endl;
-	m_connManager.addConnection( socket );
+	QPair< KStreamSocket*, void * > *connection = new QPair< KStreamSocket*, void * >( socket, 0L );
+	m_connManager.addConnection( connection );
 	
 	disconnect( socket, SIGNAL( connected( const KResolverEntry& ) ), this, SLOT( slotAsyncConnectSucceeded() ) );
 	disconnect( socket, SIGNAL( gotError(int) ), this, SLOT( slotAsyncConnectFailed(int) ) );
@@ -1623,7 +1636,14 @@
 	int fd = socket->socketDevice()->socket();
 	//kdDebug(14181) << k_funcinfo << "Socket FD: " << fd << endl;
 	
-	ret = yahoo_read_ready( m_connId , fd, m_data );
+	QPair< KStreamSocket*, void *> *connection = m_connManager.connectionForFD( fd );
+	if ( !connection )
+	{
+		kdDebug(14181) << k_funcinfo << "No connection found for socket!" << endl;
+		return;
+	}
+	
+	ret = yahoo_read_ready( m_connId , fd, connection->second );
 
 	if ( ret == -1 )
 		kdDebug(14181) << k_funcinfo << "Read Error (" << errno << ": " << strerror(errno) << endl;
@@ -1646,9 +1666,16 @@
 	
 	int fd = socket->socketDevice()->socket();
 	//kdDebug(14181) << k_funcinfo << "Socket FD: " << fd << endl;
+	
+	QPair< KStreamSocket*, void *> *connection = m_connManager.connectionForFD( fd );
+	if ( !connection )
+	{
+		kdDebug(14181) << k_funcinfo << "No connection found for socket!" << endl;
+		return;
+	}
+	
+	ret = yahoo_write_ready( m_connId , fd, connection->second );
 
-	ret = yahoo_write_ready( m_connId , fd, m_data );
-
 	if ( ret == -1 )
 		kdDebug(14181) << k_funcinfo << "Read Error (" << errno << ": " << strerror(errno) << endl;
 	else if ( ret == 0 )
--- branches/KDE/3.5/kdenetwork/kopete/protocols/yahoo/kyahoo.h #485010:485011
@@ -25,6 +25,7 @@
 #include <qmap.h>
 #include <qpixmap.h>
 #include <qbuffer.h>
+#include <qpair.h>
 
 #include "libyahoo2/yahoo2.h"
 #include "libyahoo2/yahoo2_callbacks.h"
@@ -70,12 +71,12 @@
 	 * from the connection manager and a new connection of that type is expected
 	 * to be created.
 	 */
-	void addConnection( KStreamSocket* socket );
+	void addConnection( QPair< KStreamSocket*, void * > *connection );
 	
 	/**
 	 * Get the connection by its file descriptor
 	 */
-	KStreamSocket* connectionForFD( int fd );
+	QPair< KStreamSocket*, void *> *connectionForFD( int fd );
 	
 	/**
 	 * Remove a connection from the manager
@@ -89,7 +90,7 @@
 	void reset();
 	
 private:
-	QValueList<KStreamSocket*> m_connectionList;
+	QValueList< QPair< KStreamSocket*, void *> *> m_connectionList;
 };
 	
 	
@@ -339,7 +340,6 @@
 	struct connect_callback_data *m_ccd;
 	
 	YahooConnectionManager m_connManager;
-	void *m_data;
 	
 	Kopete::Contact* m_contact;
 	Kopete::Transfer* m_kopeteTransfer;

(no debugging symbols found)
Using host libthread_db library "/lib/i686/libthread_db.so.1".
(no debugging symbols found)
`shared object read from target memory' has disappeared; keeping its symbols.
(no debugging symbols found).........................
.....................................................
(no debugging symbols found)
[KCrash handler]
#7  0x00000000 in ?? ()
#8  0xa5ec3cdc in yahoo_read_ready () from /usr/lib/kde3/kopete_yahoo.so
#9  0xa5ea2347 in YahooSession::slotReadReady ()
   from /usr/lib/kde3/kopete_yahoo.so
#10 0xa5ea3e3d in YahooSession::qt_invoke ()
   from /usr/lib/kde3/kopete_yahoo.so
#11 0xa6a93317 in QObject::activate_signal ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#12 0xa6a93113 in QObject::activate_signal ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#13 0xa715b6f8 in KNetwork::KClientSocketBase::readyRead ()
   from /usr/lib/libkdecore.so.4
#14 0xa715af5f in KNetwork::KClientSocketBase::slotReadActivity ()
   from /usr/lib/libkdecore.so.4
#15 0xa715b790 in KNetwork::KClientSocketBase::qt_invoke ()
   from /usr/lib/libkdecore.so.4
#16 0xa715ccc2 in KNetwork::KStreamSocket::qt_invoke ()
   from /usr/lib/libkdecore.so.4
#17 0xa6a93317 in QObject::activate_signal ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#18 0xa6a9340e in QObject::activate_signal ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#19 0xa6d84fb8 in QSocketNotifier::activated ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#20 0xa6aad881 in QSocketNotifier::event ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#21 0xa6a39b9f in QApplication::internalNotify ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#22 0xa6a39137 in QApplication::notify () from /usr/lib/qt3/lib/libqt-mt.so.3
#23 0xa701b19b in KApplication::notify () from /usr/lib/libkdecore.so.4
#24 0xa6a2994e in QEventLoop::activateSocketNotifiers ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#25 0xa69e4877 in QEventLoop::processEvents ()
   from /usr/lib/qt3/lib/libqt-mt.so.3
#26 0xa6a4a2ea in QEventLoop::enterLoop () from /usr/lib/qt3/lib/libqt-mt.so.3
#27 0xa6a4a1d4 in QEventLoop::exec () from /usr/lib/qt3/lib/libqt-mt.so.3
#28 0xa6a39db0 in QApplication::exec () from /usr/lib/qt3/lib/libqt-mt.so.3
#29 0x0806d7bb in ?? ()
#30 0xafbc0610 in ?? ()
#31 0xafbc05f0 in ?? ()
#32 0xafbc0758 in ?? ()
#33 0x0806d764 in ?? ()
#34 0xa6e821e0 in vtable for QGArray () from /usr/lib/qt3/lib/libqt-mt.so.3
#35 0x0829f150 in ?? ()
#36 0xafbc0628 in ?? ()
#37 0xa634b37e in operator new () from /usr/lib/libstdc++.so.5
#38 0xa6172c57 in __libc_start_main () from /lib/i686/libc.so.6
#39 0x0806d221 in ?? ()

What's your kopete version? That was fixed in KDE 3.5.1

*** Bug 124334 has been marked as a duplicate of this bug. ***