Hello Tony,
This problem will be fixed in 5.2.5, which will come out next week.
You will need to set up Paypal Login on Paypal side though. Here is the snapshot with right settings:
https://docs.google.com/a/x-cart.com/file/d/0B3WW36OSzMlZWHZCTHd6NmItdHM/edit
Tony