While I was changing lenses (my 18-70 to my 50mm), the 18-70 slipped out of my hand, hit the ground, and bounced a couple of times. There was a filter protecting the front, but nothing protecting the back. On inspection, everything seemed to be fine. I tried it out, and it worked fine. The next day when I try the lens, I mount it and on the top screen where the aperture is supposed to be, "F--" is flashing, and I can no longer autofocus. Its not the camera, because my 50mm works like a charm. Is there anything I can do to fix the lens? Upon inspection of both the front and the back, everything looks fine. I'm going on a big hiking trip tomorrow that I've been looking forward to, and I need this lens for landscapes. Its usable, because being jammed on the highest aperture and having to MF are perfectly acceptable for landscapes, I still would like it fixed. I'm getting a new lens soon to replace it, but is there anything I can do at the moment?