If I click on the current votes for a question, to show the up/down vote tallies:
Then casting a vote, either up or down, hides the up/down tallies, and the result is inflated greatly:
Additionally, re-clicking the total does not show the up/down vote break down again, unless I first refresh the page (which also corrects the inflated count).
The same thing happens if I expand the up/down vote tallies, then remove my pre-existing up or down vote.
This behavior seems most consistent on questions with at least 7 up votes, but I have seen it inconsistently on questions with a score as low as 1.
This happens in both Iceweasel (Firefox) 15.0.1, and Chromium (Chrome) 22.0.1229.94.