Every now and then - and some days more often - I'll vote to delete a question only to be presented with an unhelpful error message:
Fortunately, retrying is easy - I need only click that little red error box, as instead of dismissing itself as promised it will immediately retry... and fail.
A quick check with Firebug reveals the cause for the error: the script is attempting to post to the following bogus URL:
Note the double-slash there in the middle - a post ID is supposed to go between those.
Usually, reloading the page will correct the problem. Sometimes, several reloads are necessary. Occasionally, blood sacrifice is required.