problems with jquer 1.6.2 - "ixquery not defined"

An application i am working now uses jquery 1.4.2. i upgraded it and now i use 1.6.3. but after that i an facing some issue like dropdowns not working , cannot access the menu (ribbon) etc. it is showing 'ixquery' not defined. can any one pls help me, so that i could move with jquery 1.6.2.