Tab key changing window focus
This is one of those issues that if it had not happened to me and someone called to tell me they were having this problem, I’d probably think they were nuts! I use the tab key all the time to move between fields, so when it started switching the window focus, I started checking my keyboard to see if the ALT key was stuck as it was acting the same way Windows does when you press Alt-Tab.
After digging around, I found some posts that recommended pressing the keys: ALT-0-0-9 (press and hotel the Alternate key, then press zero, zero nine.)
This fixed the problem and now back to normal. Not 100% sure if it was the cause but I had installed an updated VMware on the system so that may have been the cause.