Version:           0.12 (using KDE KDE 3.5.3)
Installed from:    Mandriva RPMs
Compiler:          gcc-4.1.1 (GCC) 4.1.1 20060518 (prerelease) gcc-4.1.1-1mdk
OS:                Linux

I was doing nothing, nor the contact does try to send me messages, and that error box popuped up...

s/hotmxxx/hotmail/g

Here is the backtrace :
invalid length 24902
invalid length 24902
kopete (msn - raw protocol): [void MSNSocket::slotDataReceived()] ACK 13
kopete (msn): [void P2P::OutgoingTransfer::slotSendData()] Sending, 102 bytes
kopete (msn - raw protocol): [virtual void MSNSocket::slotReadyWrite()] Sending command: MSG 14 D 248
MIME-Version: 1.0
Content-Type: application/x-msnmsgrp2p
P2P-Dest: arimbourg@hotmxxx.com

#À:WB*
invalid length 24902
end from FAM server connection
invalid length 24902
invalid length 24902
invalid length 24902
kopete (msn - raw protocol): [void MSNSocket::slotDataReceived()] ACK 14
invalid length 24902
end from FAM server connection
invalid length 24902
invalid length 24902
invalid length 24902
kopete (msn - raw protocol): [void MSNSocket::slotDataReceived()] MSG arimbourg@hotmxxx.com Arimbourg 143
MIME-Version: 1.0
Content-Type: application/x-msnmsgrp2p
P2P-Dest: rapsys@hotmxxx.com

(Stripped binary data)
kopete (msn): [virtual void P2P::OutgoingTransfer::acknowledged()]
kopete (msn - raw protocol): [void MSNSocket::slotDataReceived()] BYE arimbourg@hotmail.com
kopete (msn - raw protocol): [void MSNSwitchBoardSocket::cleanQueue()] 0
libkopete: [void Kopete::ChatSession::removeContact(const Kopete::Contact*, const QString&, Kopete::Message::MessageFormat, bool)]
libkopete: [void Kopete::ChatSession::removeContact(const Kopete::Contact*, const QString&, Kopete::Message::MessageFormat, bool)] Contact not removed. Keep always one contact
kopete (msn): [virtual MSNSwitchBoardSocket::~MSNSwitchBoardSocket()]
kopete (msn): [virtual P2P::Dispatcher::~Dispatcher()]
kopete (msn): [virtual P2P::OutgoingTransfer::~OutgoingTransfer()]
libkopete: [void Kopete::ChatSessionManager::removeSession(Kopete::ChatSession*)]
invalid length 24902
end from FAM server connection
invalid length 24902
invalid length 24902
invalid length 24902
QApplication::postEvent: Unexpected null receiver
kopete (msn - raw protocol): [virtual void MSNSocket::slotReadyWrite()] Sending command: MSG 98 U 53
MIME-Version: 1.0
Content-Type: text/x-keepalive
invalid length 24902
end from FAM server connection
invalid length 24902
invalid length 24902
invalid length 24902
kio_imap: IMAP4::dispatch - command=80
kio_imap: IMAP4::dispatch - command=77
kio_imap: IMAP4Protocol::special
invalid length 24902
end from FAM server connection
invalid length 24902
invalid length 24902
invalid length 24902