FYI, for bricko and anyone else looking who stumbles across this thread, this is what worked for me with the Google Accounts cookie mismatch scenario in Internet Explorer 8 on Windows XP...

 

I had this problem for days and tried all steps I found (clearing cache, adding addresses to trusted sites, etc.) with no success. What finally worked for me was going to Tools-->Internet Options-->Content-->Clear SSL State. Suddenly everything's back to normal.

 

Hope this helps someone else out there...!