Hi,
I would look for a troublesome browser add-on or third-party security
program as the cause.

Start IE without add-ons from:
Right-click the IE icon on the desktop. Choose Start without add-ons.
or
Programs> Accessories> System tools> Internet Explorer (no add-ons)
Does the problem still occur? If not, look for the troublesome add-on.
See: http://www.enhanceie.com/ie/troubleshoot.asp
for troubleshooting information.
More at:
IEBlog  Troubleshooting and Internet Explorer’s (No Add-ons) Mode:
http://blogs.msdn.com/ie/archive/2006/07/25/678113.aspx

Turn on the Windows Firewall from Control Panel> Windows Firewall and
disable, as a test, any third-party security suite, ad blockers, other
security programs. See if a third-party program is causing the problem. If
you have Automatic Updates enabled, Windows updates would have installed in
the last few days. There may be a conflict between a third-party program and
IE7 after the updates.

Hope this helps,
Don
[MS MVP- IE]