The first thing I would check are the advanced power options to make sure nothing is putting anything to sleep (Control Panel > System and Maintenance > Power Options)
Secondly make sure you are totally up to date with all Windows Updates especially Internet Explorer because McAfee's UI is an IE page to all intents and purposes. IE9 and also make sure any add-ons are up to date.
When you reinstalled did you run the MCPR cleanup tool to make sure all traces were gone, then reboot before installing it again? It's linked under Useful Links at the top of this page.
I hate to suggest you try it again. Uninstall via Control Panel first, then run the tool, reboot and reinstall.
Other than that I can only suggest Technical Support, also linked via Useful Links up at the top. It's free by phone or online chat.
Tried all of that several times so it was always clean install
This last problem combined with multiple licence renewal issues, complete lack of responce from "support" when lodging an email support request and over large system resource use etc. is frankly the last straw.
Virus and firewall protection should be set and forget. As a business owner and network admin I simply don't have time to spend messing about any more with this sort of stuff and I am heartily sick of talking to script readers at an Indian call center.
I have been a faithful customer for 15 years and have installed Mcafee products on literally hundreds of PCs and dozens of networks but thats now over.
I can't have an important machine on the network crippled by one application and I certainly can't remove it and leave it vulnerable so I had no choice but to try another provider.
I am cancelling all our licenses and moving to Eset which actually works and doesn't kill performance every time it runs a scan.
Online chat would have probably been surer and might have sorted the issue out by now. However that's all water under the bridge. Sorry to see you go, good luck.