Bicycle Mechanics - Ultegra rear derailleur problem

I just bought a used Gunnar Crosshair cyclocross bike. It has Dura Ace shifters up front, a Shimano 105 front derailleur and a Ultegra rear derailleur. When I bought the bike I rode it and shifted it and all seemed well. But on my first ride with the bike I noticed that the rear derailleur shifts weird. It does not skip or shift badly, but it takes two clicks of the shifter to change gears. If I am shifting up for example I click one at a time and all is well. But then I change and want to shift down I have to click the shifter twice and then one at a time after. I had a friend look at it and he tried taking slack out of the cable, played with the adjuster screws. My friend had no luck and said there was a problem with the shifters. The chain and rear cassette seem to have alot of wear, that could be a problem. But why would it seem like it a 10 speed. Could there be a 10 speed derailleur on a 9 speed cassette? The shifter are 9 speed shifters so why do they click 10 times? Does anyone have any ideas?

9 speed rear shifters should only click 8 times. If the chain and cassette are really worn, replace both before you go wasting much more time with the shifting problem. Might as well replace your derailler cable and housing while you're at it. Then follow the procedure at www.parktool.com (http://www.parktool.com) for setting the limit screws and adjusting the cable tension. Your friend likely made things worse by playing with the limit screws without really knowing what he was doing (because if he did know what he was doing, those would be the last things he touched).

Whenever I encounter a rear shifting issue that doesn't respond to normal tuneing, the first thing I do is to check the derailleur hanger alignment. Almost always - that's it.