Let McAfee fix this. The most common fix is to uninstall what you have and get their latest.
I have a new dell inspiron purchased in Dec.09. At that time it had McAfee for a 30/60 day free trial on board. However when I went to download McAfee from my 3 user account, the computer would not boot up normally. I had to use F12 key and backdoor to get into my computer.t. Dell representatives couldn't help. McAfee finally agreed, working on the problem but after much discussion. Other applications failed.