IRRITATING ticking sound in one gear and chain slipping in another
 

I am a new cyclist and I have a brand new Trek 2100. I have not crashed it, gotten any flats, hit anything nasty (maybe one or two potholes) or done anything to damage the bike. It basically is driving me crazy. In the middle gear on the cassette (it is a 9 speed ultegra triple) and the middle chainring the chain jumps off of the gear in the back and up to the lower gear and then back down in the middle of pedaling. It is not fun to have a huge CLUNK come out of the bike as well as a loss of "resistance" in the pedals.

The second problem is an insistent ticking that I have when I am in the fourth smallest cassette and any gear up front. It seems to make this horrible ticking sound- it is not a high pitched but a low pitched sound and it varies with the speed of pedaling. It ONLY happens while pedaling in this rear gear.

Both of these problems happen after either shifting up or down into the given positions. The shop has dealt with it three times and I am ready to quit riding it. I am taking it in tomorrow and I never want to take it in again.

What is the problem?

Thanks for any help

Colin

By the way, the shop has adjusted the deraileur each time.