I've noticed this bug for a while now: whenever I cast a vote on a question or answer in StackOverflow, then proceed to navigate to another page or refresh the same page (within roughly 5-10 seconds), I observe that my vote has disappeared. This is somewhat irksome in that it forces me to wait for at least 10 seconds before closing any page on which I have just voted.
This would seem to be a bug in the AJAX functionality of voting, and I suspect there is no technical reason for this behaviour. Surely it's not taking up to 10 seconds for the AJAX request to be sent. (My internet is running nice and speedily otherwise.) I should note that this has happened for me in Firefox 3.5, though I haven't tested on other browsers.
Can anyone else confirm this bug? It would be helpful to have it fixed in the near future.