try sticking a flat blade screw driver inbetween the tank and the plastic and twist it while you try to take it out maybe that will apply enough pressure to make it come out.
Try searching...This has been brought up many times and there are some good solutions out there.I'm having this problem on both of the bolts on my 05. My 07 that I had had one of the bolts do it. Any other ideas or solutions? Tried the flat head deal as well. Don't have any vice grips handy. Thanks![/b]