Anytime you install this many new parts in a drivetrain (especially if you did something like change the gearing), you have to go through all the adjustments to get it to work correctly - cable tensions, high/low limit screws for both derailleurs, indexing, chain tension, b-screw, etc. The fact it is derailing off the small sprocket means, at the very least, that your high limit screw is off which tells me that you probably adjusted little or nothing. So you need to go through these adjustments or if you're not qualified, find a mechanic to do so. You still may have a problem, but until these adjustments are made, all bets are off.

- Mark