I just asked on the mechanics forum but since the original thead was here I thought yall might want to advise because not everyone checks out the mechanics forum often (well I know I dont).
My bike is a 520 with bar end shifters. I flipped the bar upside down so I had to remove the shifters and breaks and put them back on. Now when I am climbing the mountain in granny gear the chain or something is slipping when i get to a real steep section and have to peddle hard. Just from flipping the bike over and running it down to the smallest gear it lookes like the rear deurailer is over far enough. I can go up one gear and it does not slip. I have not tried to adjust anything but it is agrivating. I can make it up the mountian in the next to lowest gear but it is harder. BTW here is the thread from when i flipped my bar. As you will see, I am not a bike machanic.
The problem might be cable friction, put a bit of grease around the bare cable where it goes under the BB.
See if that fixes it. I had a similar issue riding 26x30 and 34 and the grease did the trick
You could have some damage. It's also possible this was just the point when the chain seased. Just a coincidence. For that you need to go over every link pair, and flex them to see if any bind. Then add some oil.
i think i might have had a similar problem a while back.
have you tried to tighten your shifting lever things?
theres usually a place at the base of the lever for a hex key or something. give it a few turns to tighten it up, and it should keep your stuff from slipping.