Running Windows 8.1 and last night first on my Toshiba laptop and then on my HP desktop McAfee had been turned off and I was not able to turn it back it on. I had to re-install the software. Virus?
and run this scan on both machines to check for any McAfee related issues. I might also add you need to be up to date with all Microsoft updates and IE even if you choose to use a different browser so keep those updated as well. Adobe and Java if you use them should be current too.
It is possible that there could be some sort of virus or malware lurking but if it happened to both machines at the same time might lead me to believe there may be some P2P software (sharing files) and this could be the cause.
Let us know what you were able to find out with your issue.
McAfee Volunteer Moderator