I've brought several issues to the KTorrent forum, most of which were not the responsibility of KTorrent, but a couple were. I recall a couple of glitches such as application crashes any time all torrents were paused.

I've been running 4.0.4/1.0.4 for a while now and I'm not aware of a single flaw. The client runs smooth and stable.

Thank you for all the hard work and thanks again for the assistance with the issues.

I can confirm that ktorrent 4.0.4 crashes if a few selected seeded torrents paused and after that started.

Do you have a backtrace of that crash ?

No backtrace because it is hard to reproduce this crash.
Sometimes when paused torrents started appears error message about file that can not be opened.
But this error appears only for some of paused torrents, other are started.
This error also appears for not paused downloading torrents when starting paused seeding torrents.
If then I press start on torrent with error it started without error.
And sometimes this error message appears at KTorrent start.
Sometimes paused torrents starts immediately without errors but sometimes after long delay and then this error appears or crash.

There is bug report against ktorrent 4.0.4:
https://bugzilla.redhat.com/show_bug.cgi?id=652708

Unfortunately no additional information about this crash only backtrace was provided there.

Looking at that backtrace, it's either a Qt bug or KHTML bug.