Screensaver/PowerSave disrupted by program - how to track which one?

[poisoborz]

Hola,
I have a very annoying problem - Win7's LCD power save mode, after a few minutes, gets constantly disrupted by an application. As this happens with detached mouse and keyboard, I think a process might be the culprit. But how can I know, analyse which one? Are there "usual suspects"? Is there a system log entry for that?
Thanks

 

[alyoshka]

I think it might be file sharing.....