SquareUp plugin breaks user registration on checkout

Has anyone experienced any issues with the SquareUp payment plugin breaking user registration at checkout?

I have my store configured so only registered users can checkout (meaning they get given the oportunity to register at checkuout). This works fine for both the PayPal and Offline payment plugins; but the second I publish the SquareUp plugin to the same (default) customer group, the Registration button hangs and users can't get any further.

Is this something anyone else has come accross?

It's a pity support don't seem to want to help wih this one...!

Dear Stuart,

Just want to mark that problem was resolved via ticket system.

Sincerely, Giang