I just did some voting on some new questions, and this appeared:
I often reach my vote limit, so I was not surprised, however, note that I have only issued 36 votes today. Is there some specific restriction that I have triggered, or is this a bug?
The vote limit used to just be 30 votes in a day, but it got a little more confusing when they added 10 extra votes for questions (and then changed it) to try and encourage question voting. Now you can get up to 40 votes in a day (30 regular votes + 10 extra question votes), but once you're low enough on regular votes to start getting the "you're nearing the vote cap" warning, that's it -- you have that many remaining. So you can end up not getting the full 40 depending on the order you vote on things