It's related here:
https://bugs.launchpad.net/ubuntu/+sour ... bug/175494

"When running KTorrent in gnome it starts a process of mplayer which consumes all cpu resources. When you close KTorrent the MPlayer process does not stop and it cannot be stopped. As soon as it's killed a new process starts. The only way to stop the runaway process is to log out of gnome."

Have you tried compiling the program yourself? Because in the time that I have run ktorrent I have never had ktorrent spawn mplayer unless I chose the preview option (I think now it is labeled Open). This problem may be something with the ubuntu package.

Also an FYI... I was noticing on the forum that people were wondering why it was mplayer. When you select Open/Preview on a torrent ktorrent uses KDE's File Associations to select what program to use. So you were probably downloading a video and mplayer is the default application for that file type.

A quick question... If you open up the kde Task Manager and click on the tree option, what program spawns mplayer after you have killed ktorrent?

Yes, MPlayer (specifically SMPlayer) is my default application for that file type in an Gnome desktop (Ubuntu 7.10).
This never happened until yesterday.
I used to made KTorrent my torrent application for a long time and I never had any problem with it.
Then I looked for answers in the Google and found that it was already reported in Ubuntu Forums.
It wasn't me that post it in launchpad.
I thought to open the source code and comment or remove any kind of system call that calls a video player...

It should never call it unless you specifically right click on the file and select open. That is why I asked if you compiled it yourself?

Like I said, I have used this for a long time without a problem.

Have you looked into any of my other questions?

That's very strange.

The only time when we fork another process is when you manually do that in the files tab. KIO will also fork a bunch of slaves to do it's work, but those should not trigger mplayer.

Also ktorrent itself will fork to detach from the terminal, this can be avoided by doing ktorrent --nofork, but that also should not trigger mplayer.

I compiled it myself, but the problem instill on.
In Ubuntu Forums a guy called puterman discovered that:
"I did some digging and discovered that the problem was with trackerd, which indexes files in specific directories, by default your home directory. So if you download your torrents to your home directory (or any subdirectory), trackerd will keep scanning the files repeatedly while they're being downloaded, using mplayer for video files. (Continually scanning the files in this way seems like a bug to me.) The brute force way of fixing this is to kill trackerd. The less brutal way would be to configure trackerd to not scan your torrent download directory. See the man pages for trackerd, tracker.cfg, tracker-search-tool etc. for more info."
I will try to reconfigure the trackerd to do scanning my torrent folder to see what's happen.
Thank's for the help!