I had a similar problem but this was with sp2 installed.
Try opening IE click on tools>advanced and click the reset defaults button then click apply>ok and restart IE.
You could also allow auto update - when I couldnn't access the website this still worked.
If these fail it could be that your profile is damaged - microsoft's solution is to delete the profile but you can imagine the chaos that causes! So just setup a new administrator account and just use that fow win updates.