Another thing to try: clear out your temp files and cookies. We recently changed our cookie system slightly, but with the side effect that all existing cookies were considered to be invalid. It's possible that an existing cookie is affecting the new cookies.
You can also try upgrading to the beta branch of Chrome and to Firefox 4 to see if that changes anything. I wouldn't recommend keeping them forever, just do it as a test then downgrade.
Check to see what extensions/plugins you have installed for each browser to make sure there isn't anything that might affect page load.
Finally, run some anti-spyware and anti-virus apps to see if there's anything that could be affecting your system.
Bara
