I've got a bounty quest to kill the bandit leader at a cave in Whiterun but when I arrived at the cave I'm unable to enter it. I see the quest marker on the entrance and walk up to it but then can't enter. I've entered that cave before so I'm not sure why I'm having this problem now. Also I made a test character and he can enter the cave no problem.

I've saved the game quit out and re-loaded it to see if it would solve the problem, didn't help.
I've fast traveled to and from the cave, didn't help.

Any fixes?

Edit: This is what the cave looks like http://i1305.photobucket.com/albums/s544/BSAroyalty/2013-01-15_00002_zpsafeebfc4.jpg & http://i1305.photobucket.com/albums/s544/BSAroyalty/2013-01-15_00003_zps30dbdc73.jpg