Welcome to the forums, this is probably a question for the "mechanics section"
Anyway, i`m on this with Steele-Bike , check also your cable tension and your front derialleur adjusment, if you want to do it yourself, but don`t know how it works, look at this link -->

http://www.parktool.com/repair_help/...ex.shtml#frame

They give step by step advice and orders how to do all sort of maintenance on bicycles, good luck,

Regards,