You already have a bounty set on one of your questions: Is there a free (or very cheap) tool for highlighting changes in data for sql server?
The rules, as stated in the faq, is that a user may only have one active bounty at a time.
The question has probably already had a bounty, which expired unawarded because no answer had a score of 2 upvotes or more.
Sadly, for those questions it is not possible to award a new bounty for some reason; under the old system, it was not even possible to accept them any more. They will remain unaccepted forever, which in my eyes is a bug.