Purchased a brand new chain EXACTLY like the one I've had on my bike since I bought it. The chain that came with the bike when it was brand new was a Shimano HG53 and its worked fine for a couple of years with frequent cleaning. I purchased the exact same chain (according to whats stamped on the links anyway) and put it on according to the instructions. Go out and pedal and the chain skips on the rear gears- badly...like many times per pedal revolution. This is the second time I've run into this problem. I tried to replace the chain about a year ago and got the exact same results. The chain I bought that time was also Shimano, but it was one of their more premium chains. This time, I figured if I bought the exact same chain that came with the bike I'd be okay. Same problem. The rear gears do not appear to be worn excessively, and the chain did not have any tight spots or kinks in it from assembling it on the bike. So its back to the OLD chain... again... that is eventually going to leave me stranded in the woods one day. Any ideas what the problem might be? Has anyone else experienced a similar problem? The bike's specifics are: Bianchi IBex, SRAM X-7 derailleur and 9 speed freewheel, Shimano HG 53 9 speed chain.