Going by your signature that you are running Microsoft Security Essentials and Windows Defender
Microsoft Security Essentials is not compatable with avast!
I would also update to at least IE8 and preferably IE9.
I've been running Avast along side ThreatFire, Windows Defender AND Security Essentials for ages and they all played nicely
UNTIL the last
PROGRAM update.
In fact I am running 5.0.677 right now DUE to flawed code in that last update on a Windows 7 x64 machine.
Why is everyone at Avast swearing it is NOT the last program update that is the problem rather than that of users?
By the way, in attempting to make the last program update work disabling the other applications didn't change anything.
I paid for Avast Pro for years, when I owned my business, but am now thankful for the FREE service afforded by Avast to home users so I am NOT an ungrateful user.......but I won't be blamed for somebody else's mistakes either. Things happen and this time something happened.
Fix it and be done with it so we ALL can update the program without going
bonkers again.......