Had a bad fall a couple of days ago, bunnyhopped on a downhill off a small bump and did not land it, bike seemed fine after the crash, 2 days later went for a ride again and it started to rain and got quite muddy during the ride, took a corner too fast in the mud and the front wheel washed out and the bike went down, nothing major, just a small slip. Looked at the bike, everything seemed fine...again...about 5 km later I shift...and nothing, back derailer(shimano alivio) is not changing gears at all so I took the chain and put it on a gear that I can finish the ride with, 1km later gears starts working again. Took the bike home, everything works. Give it a nice wash and yesterday when I hook up with some buddies same thing happens no gears, just this time it does not come right, the cable that goes to the back derailler got no tension in it, so I unscrew it a little at the back derailler and pull it tight, change gears, chain stays put, and the cable goes slack again. It seems I might have bended the arm hanging down from the derailler(what do you call this arm?) slightly. Bought a new fork this month, so no cash to fix the back derailler or get another one, I want to upgrade to SRAM X09 next month anyway. Thing is I got a night ride tomorrow with a group of mtb riders in my town for the first time. Anyone got a suggestion as to what can possibly be wrong and how I can fix it?