This is happening on a friend's new computer...and was happening on the his old computer, too.
Old WinXP computer- Working in one application, say Word 2003, while Firefox is open. All of a sudden active window switches to Firefox. Very aggravating. Would switch from other applications as well. No need to go into detail, but I tried EVERYTHING to resolve, but to no avail. I thought it was either my friend (87 years old) or some weird hardware glitch.
Brand new Win7 Dell computer - using Office 2013 now, and all brand new installations of everything of course. Same thing is happening, and that this time it's happened to me several times while I've been remoted in with LogMeIn.
After installation of new computer, I connected his old HD to the new computer with USB cable to copy his data. Maybe some malware or root kit infection migrated to the new computer?
Multiple scans with multiple big name scanners found nothing!
It's a pretty vanilla system with the following programs in use:
HP OfficeJet printer & software
Eudora for e-mail (no comments please! :-))
Startup programs are VERY clean!