Forum:Problem after playing co-op

Hello can you help me please? I dont know where to contact people for Borderlands troubleshooting. I bought Borderlands GOTY version and finished the game on singleplayer and the Zombie and Armoury DLCs, then I played online for a while and some of the missions Ive either gone through already or missions from Claptrap DLC copied to my ECHO without me accepting them. Now when I arrive to Claptrap DLC area for the first time I cant get through the door under the sattelite because when I talk to Tannis, I have only the missions which act like being accepted by me but they werent. Furthermore, there is no hello from her or explanation or opening cinematic or what should be there. Now I cant play the DLC. Is there a way to erase missions which are in progress? Or how can I get rid of this problem and be able to play the final DLC? Thank you very much