OK, I think I've figured it out by systematically closing programs running in my tray. There seems to be an incompatibility between FPV and a program called Actual Windows Minimizer. See:http://www.actualtools.com/windowminimizer/
FPV will not start up properly, for me anyhow, if this program is running. If I exit Actual Windows Minimizer, launch FPV, then relaunch Actual Windows Minimizer, they seem to get along.
So a work around for me is to not use one or the other program, I guess, but this is far from ideal since I'd rather be able to use both.
I'd still appreciate any suggestions.