For the archives (since an answer has already been accepted.)
IE Slow Down.
With IE8's RTW release, users of the popular anti-spyware tool SpybotSD started having serious problems with IE's speed (from working as normal in the Beta and RC stages) to taking X minutes for startup and creating new tabs.
A problem was identified/highlighted by Safer Networking authors of SpytbotSD with IE8's handling of extremely large lists in the "Restricted Zones." Safer Networking's press-release references a Microsoft fix at KB969897 (released June 19th, 2009.
The finger pointing aside (as blame can be evenly divided between MS and SN) if you're having the speed issues and have SpybotSD installed, check the above references or update both pieces of software to their 'current' renditions as the problem seems to have been resolved.
- SpybotSD "Immunize" feature stuff's IE8's Restricted Zones list with a lot of sites.
- The list isn't designed for this use (abuse?)
- MS Changes the base code used within the Restricted Zones functionality to support new web standards directions.
- "Restricted Zones" feature slows insignificantly for a short list, but significantly for the huge lists generated by SpybotSD's "Immunize" feature.
- Do not use IE8 -or-
- Disable SpybotSD's "Immunize" feature (i.e. if you've already used it, undo it!!)
- Use IE8's "Smart Screen Filter" (use it anyway, even if you want to use SpybotSD.)
I run 'current' versions of IE8/SpybotSD and Windows 64bit 7RC1 without problems, where I remember disabling spybotsd to get IE8 RTW functional in Vista 32bit.