Version:           2.1 (using KDE 3.5.6, Kubuntu (feisty) 4:3.5.6-0ubuntu14)
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.20-16-generic

at the beginning, I thought ktorrent crash because it was loading a file. But it is crashing also whith no activity at all. With one or more files loading, without activity: at any time, it can crash. I can't remark any regularity in the crash.
Here is the debug report:

(no debugging symbols found)
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
[Thread debugging using libthread_db enabled]
[New Thread -1235097904 (LWP 5683)]
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
(no debugging symbols found)
[KCrash handler]
#6  0xb7e79bcb in dht::ParseRsp () from /usr/lib/libktorrent-2.1.so
#7  0xb7e79df2 in dht::MakeRPCMsg () from /usr/lib/libktorrent-2.1.so
#8  0xb7e6ef51 in dht::RPCServer::readPacket ()
   from /usr/lib/libktorrent-2.1.so
#9  0xb7e6f252 in dht::RPCServer::qt_invoke ()
   from /usr/lib/libktorrent-2.1.so
#10 0xb6eb388b in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#11 0xb6eb4330 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#12 0xb763d04c in KNetwork::KClientSocketBase::readyRead ()
   from /usr/lib/libkdecore.so.4
#13 0xb763d086 in KNetwork::KClientSocketBase::slotReadActivity ()
   from /usr/lib/libkdecore.so.4
#14 0xb764f143 in KNetwork::KClientSocketBase::qt_invoke ()
   from /usr/lib/libkdecore.so.4
#15 0xb764f1e6 in KNetwork::KDatagramSocket::qt_invoke ()
   from /usr/lib/libkdecore.so.4
#16 0xb6eb388b in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#17 0xb6eb41a2 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#18 0xb7240877 in QAuServer::qt_property () from /usr/lib/libqt-mt.so.3
#19 0x08333658 in ?? ()
#20 0x00000002 in ?? ()
#21 0x0000000e in ?? ()
#22 0x00000000 in ?? ()