Download the latest version of MVT from here 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.
You may also consider running some of the excellent programs inAnti-Spyware/Malware & Hijacker Tools to check for any infections. Run McAfee Stinger and also run Getsusp.
If there is an issue with the software itself contactMcAfee Consumer Products - Types of Support specifically Technical Support and they could remote connect into your machines to see what is happening.
Let us know what you were able to find out with your issue.
McAfee Volunteer Moderator