Why do I get logged out after a while of innactivity?

[amgeex]

After a while of innactivity my system logs me out and takes me back to xdm. How can I fix this?

Also, each time I get logged out my wallpaper resets to the style's default. How can I stop whatever-is-doing-this from doing it?

Using debian 3.0r1, blackbox "stable" package, mozzila sid, default xdm.

[bandwidth_pig]

Are you logged out or is the screen just locked?

[amgeex]

I get logged out, and back to xdm's login screen (the ugly one).

[amgeex]

Some help/hints/tips here, pleez? ;p