The chain ring on my wife's fixed gear is out of round. When I try to slow down I notice the time it takes for the chain to pick up tension in the other direction. The variance in the chain tension has now causes very high tension on one side and visable slack on the other. There is also some gear noise that I consider louder than normal. I finally tried turning the crank to the loosest point on the chainring, moved the wheel back as far as possible (the crank would barely rotate) and then loosend the chainring and tightened it again. That may have helped a little.
I took it to the best local bike shop and asked the guy to straighten the chainring. He wouldn't do it because he said they are all out of round. I am going to trust his advice for now, but I'm curious what signs I should look for in the future. I don't want my wife to get stuck 5 miles from home while I'm at work.