See the Last checked flag not updating? thread for a detailed explanation of why you might not get your votes every once in a while. The discussion is about another type of update but the reason and the explanation are the same for both cases.
The new-year vote allocation failure was a much rarer problem that probably affected everyone (it looks like the failure was right at the start of the script, but that was a quick look so some might have gotten votes). The job that allocates new votes (aka the vote fairy) failed because the SQL database was too busy.