Where I work we have several hundred computers and McAfee, useful and necessary as it is, has often caused us reliability and other problems. I would suggest that you a)reinstall and then properly uninstall McAfee; b)run SCANDSKW and run it all the way to the end (may take a couple of hours if you have a large HDD and have never done it before); c)run DEFRAG and uncheck the setting option to arrange files so that programs start faster (also may take a while). After that, run Norton utilities Win Doctor.
THEN, reinstall McAfee, and make sure that it does not start and run automatically. You can always invoke it from time to time (and you should). But that way, it will not hang up your boot routine or cause operational problems while you are computing. After that, make sure you get the updates so you can be as current as possible, since there are many virus writers who don't have music in their lives, but instead put their energies into making others miserable. :-(
Funny that this computer thingie needs so much baby-sitting. I first got into it so that I could write more efficiently than with a type-a-writer. If my guitar were this demanding, I would have to seriously reconsider that.