i just had them try: http://livetest.ubercart.org
and it DID redirect to their cart and add something to their cart....
so it must be something about my site...

the test site is in dev at:
http://avoidremodelingnightmares.yestrainingandeducation.com/

i doubt it would be because i'm still in paypal sandbox mode.. because adding to the cart should not have anything to do with paypal...

if you try it, could you post if it redirected and added to the cart properly?

Thanks a ton!