I've noticed an asthetic bug on SuperUser - I'm not sure if it affects any other sites. Basically, I've reached the daily voting limit, and clicked on the vote up button. While an error was received, the vote count and "depressed" image stayed until I refreshed the page.
This could confuse possible users of the site, as they may be left wondering whether their vote was processed. Especially since we're not dealing necessarily with programmers and sysadmins - users who may not be completely comfortable with computers.
I don't think this is a bug with SuperUser as it is more of an issue with all of the sites. There are numerous times when you use the sites and the up or down arrow will be displayed as marked even if you aren't marking it anymore. This can be anywhere from marking and then getting an error (as you stated above) or marking, then taking away your vote, then backing to another page and then forward again. I don't necessarily think this is much of a problem and I don't find it that confusing. If it does get confusing, people will just refresh the page and then see whether or not their vote was actually counted.
I also have the same issue. I'm certain it's not a bug, though it is a nasty "feature" that I'd prefer was not a part of the private BETA, given the standing of those participating in it. Perhaps we could increase the limit during the BETA and/or for those with a certain level of reputation or some other metric?
I worked it out. 30 votes per day is far too few IMHO.