Re: Mystery Issue... Generator/Alternator?
I'm assuming you had the charge/batt indicator happening before the belt change.
It's always possible the belt was the fix, but maybe it's starting to slip at the higher rev's.
Couldn't hurt to go back in and check, or re-tension.
Not sure about the alternator, but I'm guessing if borderline, you might see some indication when toggling power for things like high beams, or windows.
I hate when crap like this is intermittant, fixing is so much easier when it fails hard...