Is this Windows 7 SP1 and do you have IE9 installed and fully updated, whether or not you use it? McAfee relies on that even when you use another browser.
Do you have any other security software installed or previously installed that may interfere?
Also are you logged in as an Administrative-level account?
Is your connection an 'always on' type?
It could feasibly be simply a question of the servers being busy so if it continues Technical Support is free and a phone call away if you need them
Check the link under Useful Links at the top of this page.