Plus/minus keys (+/-) for upvote/downvote not working in Firefox 15

Hi, has anyone noticed a bug where the +/- for upvote/downvote doesn't work on Firefox 15? I don't have another machine with Firefox 15 installed so I don't know for certain it's a bug, but I tried running Firefox in Safe Mode and the functionality was still gone. It works in Google Chrome and IE on my computer, so I don't think it's my computer. If you could take a look at it, it'd be great, thank you! imgur love <3