I have not heard of pages only half loading being caused by a virus of some sort but when you say you are unable to log in to Macafee that can often be a symptom of a virus.
You appear to have tried all the immediately obvious checks and so my next move would be to go
here and follow the simple and comprehensive instructions to the letter. If your problem prevents you downloading some of the needed files then a workaround is to download them on to a memory stick using another PC.