I have the same problem although I think when you see the submissions vote go up it's someone else since they get voted on a lot more than individual comments. For me it's both in chrome and firefox (in Win 7) so I don't think it's the browsers faulth and I noticed it for the first time maybe a 15-30 days ago. I'm guessing one of three things are happening:
1) We banned from voting as the moderators doesn't seem to tell people when they moderate.
2) pg is running an experiment.
3) It's a bug.
I agree that there needs to be a place to report malfunctions. It would also be nice to know when a moderator takes action against you.
Same had happened to me. My guess is that not informing you that you can't vote is intentional. It's like making troll comments disappear but not letting the troll know.
1) We banned from voting as the moderators doesn't seem to tell people when they moderate.
2) pg is running an experiment.
3) It's a bug.
I agree that there needs to be a place to report malfunctions. It would also be nice to know when a moderator takes action against you.