I've never had a discussion about mentoring without someone offering a story about the mentor from hell. Stories of micromanagement, hostility, uninvolvment or just plain weirdness are some of the tales of woe from the mentees.
The most difficult situation is when the mentee can't find a way to put an end to the relationship. Finding a way to be diplomatic and not totally sabatoging a career while ditching a mentor at the first opportunity can be tough. Most mentees don't want to be disrespectful or unprofessional, but sometimes horrible mentors can push them to extreme measures.
I've written before about finding a mentor and making sure you both get something out of the deal, but is there a way to spot potential "bad" mentors before you enter into the relationship? Is there a way to check out the credentials of a potential mentor before you make the commitment? And, if you do find yourself disliking your mentor, should you just give it more time or get out as soon as possible?