screen saver problem

I have a friend / client who has just bought a new system with a sempron processor, 512 mg ram & 80 gig HD running XP home. When he boots up, the screen saver never comes on (set for 10 mins)even after running all night. If he logs on to the internet for even a second, then logs off, the SS starts working. He has run Adaware & spybot & now has CA sotware running. Any ideas?
Gazza