One other (less pleasant) possibility is having a virus which interferes... but that's less likely. BTW, even if you scan with 2 AV's (better to scan with 5 - online scanners), you still might miss some.

of GAWD, Doc!{let us HOPE it isn't a virus/malware}I think not, tho...fingers crossed.....my system is clean on last scan(with all the hacking lately I thought perhaps THAT was the culprit)

Rather than whitelist anything, I just disabled all my extensions but still can't post a comment to a skin.  Behavior when left-clicking 'Submit' is the same, just jumps to the top of the page without 'submitting'.