Some Malicious Softwares (Virus/Spyware) may cause this symptom, though usually doesn't permit updates to occur at all. Consider rebooting into safe mode and running an AV scan and reviewing your startup items (Start Menu, Registry) for items that do not belong.
Combofix is my favorite tool for cleaning up malware:
http://www.bleepin





by: jrathiPosted on 2009-05-19 at 13:30:08ID: 24426300
is your windows genuine? i have seen non genuine windows wont do any update