Version:           2.1 (using KDE 3.5.6, Kubuntu (feisty) 4:3.5.6-0ubuntu14)
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.20-15-generic

This is happening only now when I updated into feisty not before.

Maybe is something with tracker, because one torrent recently reported tracker status with "server late, the connection should be on www.xxx.com" and not "OK" as should be.

Here is bug report ktorrent gave:

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Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
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[Thread debugging using libthread_db enabled]
[New Thread -1235084656 (LWP 7282)]
[New Thread -1263019120 (LWP 7292)]
[New Thread -1252582512 (LWP 7283)]
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[KCrash handler]
#6  0xb7e7cb9b in dht::ParseRsp () from /usr/lib/libktorrent-2.1.so
#7  0xb7e7cdc2 in dht::MakeRPCMsg () from /usr/lib/libktorrent-2.1.so
#8  0xb7e71f21 in dht::RPCServer::readPacket ()
   from /usr/lib/libktorrent-2.1.so
#9  0xb7e72222 in dht::RPCServer::qt_invoke ()
   from /usr/lib/libktorrent-2.1.so
#10 0xb6eb688b in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#11 0xb6eb7330 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#12 0xb764004c in KNetwork::KClientSocketBase::readyRead ()
   from /usr/lib/libkdecore.so.4
#13 0xb7640086 in KNetwork::KClientSocketBase::slotReadActivity ()
   from /usr/lib/libkdecore.so.4
#14 0xb7652143 in KNetwork::KClientSocketBase::qt_invoke ()
   from /usr/lib/libkdecore.so.4
#15 0xb76521e6 in KNetwork::KDatagramSocket::qt_invoke ()
   from /usr/lib/libkdecore.so.4
#16 0xb6eb688b in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#17 0xb6eb71a2 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#18 0xb7243877 in QSocketNotifier::activated () from /usr/lib/libqt-mt.so.3
#19 0xb6ed944a in QSocketNotifier::event () from /usr/lib/libqt-mt.so.3
#20 0xb6e4da60 in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#21 0xb6e4f88f in QApplication::notify () from /usr/lib/libqt-mt.so.3
#22 0xb7611ce2 in KApplication::notify () from /usr/lib/libkdecore.so.4
#23 0xb6de01e9 in QApplication::sendEvent () from /usr/lib/libqt-mt.so.3
#24 0xb6e3fe59 in QEventLoop::activateSocketNotifiers ()
   from /usr/lib/libqt-mt.so.3
#25 0xb6df4d07 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#26 0xb6e68136 in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#27 0xb6e67f46 in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#28 0xb6e4f609 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#29 0x080653d6 in ?? ()
#30 0xb6667ebc in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#31 0x08064ec1 in ?? ()