Wow! On the first 5 forums I've registered to, I have an average of ½ reply in a couple of days
I'm currently at work so can't tell about my Windows 7 build - don't remember.
The last software I installed was Photoshop CS3 two weeks ago - much before the problem appeared.
But I've updated Windows with a critical update - new definitions for the... mmm.. forgot its name... some kind of protector

I've AVG 8.5 Free installed - I think it was the first appilcation I've installed on the system and before the problem has begun I hasn't updated it, so I don't think it's related to the problem.
I haven't ran any registry cleaners yet.
So... my actions when I return home:
1) finding out my Windows build

2) deleting my pagefile
3) disabling my AVG
Before steps 2 and 3 I'll check if the problem persists.
I'll report if something helps.
Thank you all!