Just the other day I could cast 38 votes, then yesterday I could only do 32. Is there a factor affecting our vote limits? Perhaps like saving-up?
What reported by @MrHen is correct. The limit is 40 votes but, for what I have noticed, you need to vote 10 questions before you vote for 30 answers.
For example, if you vote 2 questions, and then vote 30 answers, then you already reached your limit.
The order of the votes is not important; you could vote 4 questions, 15 answers, 2 questions, and 15 answers, and you would have reached your daily limit.
The FAQ reports the following sentence, about voting:
A maximum of 40 votes can be cast per user per day, however, to reach the maximum you must vote on at least 10 questions.
1Almost there. Check out this answer by one of the devs for how this is actually implemented. May 12, 2011 at 9:39
This was changed per a blog entry:
The daily vote limit used to be 30 votes per day; we’ve increased that to a maximum of 40 votes per day — but only if you vote on a combination of answers and questions. This isn’t as significant as you might think, since it is exceedingly rare for users to even hit the 30 vote daily cap.