Error code on checkout using marketpress & appointment plus

Hi,

I am getting some error code on checkout see screenshot attached – http://monosnap.com/image/h1X9ESiNg88GlcUkFz1wg40nGNDSPM

on this page – *URL(S) REMOVED*

actions:

1. created new user

2. book an bike

3. select appointment

4. Continue to checkout then get error

any help would be appreciated

thanks

Tom