Help! can't get gas tank open

[Mandres]

Update:

ok tonight I drilled out the lock and found out what the problem was.  On the bottom side of the gas cap is a flange that moves in and out as the lock is opened/closed and holds the cap to the tank.  This flange mechism is hopelessy clogged with a couple of years worth of crap; it's totally frozen.  In the process of disassembling the unit further I also managed to destroy a gasket on the underside.  It's time to call it a loss and source a replacement on e-bay.  Thanks for the help everyone.

-M