Whoa! Don't go emptying your MP. Perhaps it has something to do with MP, (I haven't had any trouble finding it, so I didn't notice) but I know it's not empty MP...I definitely would have remembered that.

I mentioned this in another thread, but:

After accepting a hunt try talking to the poster of the bill again, they might give an extra hint. And if you're still having trouble, talk to the guy on the counter behind Montblanc at the clan hall. He'll mention your hunts at random, and give more clues (usually as much info as you need) as to where and/or how they can be found.

Happy hunting!