There is no one size fits all when it comes to computer security. What works for some people may not work for others.
Since the issue began after you installed McAfee it is possible that McAfee doesn't play nice with your system.
The solution is to uninstall McAfee and use another firewall and antivirus.
I installed McAfee on a computer I had years ago. It made my system crawl slower than a turtle. The only way I could get rid of it was a format and reinstall of XP. Drastic measure for me to take. You should be able to use Add Remove programs to get rid of it. After the uninstall, run the McAfee removal tool found here:
http://service.mcafee.com/FAQDocument.aspx?id=TS100507
If installed on other computers, you can leave it if there it isn't causing any issues.
If you want to purchase a program, BEFORE purchasing and installing it, go to the website for that program. See if there is a trial use offer. If there is, install and use it in order to find out if/how it affects your machine. This will also allow you to evaluate the program features-is it easy to use and understand?
It will not take you long to find out if it would be a good fit for your system.
You could also switch to free a free firewall and antivirus.
A list of recommended free programs can be found here:
http://www.bleepingcomputer.com/forums/topic3616.html