I am not sure the category “how do i” would be suitable either, since the problem is not relating to usability but it looks more like a bug.
I will try to give you a further description to the problem:
If a user comes to buy something for the first time they are asked if they want to register or check out as a guest.
Lets say the user types in their registration details and move in step by step to the final page before it is redirected to the paypal payments standard uk page, the problem starts when the redirected paypal website loads up and the price information has not been transferred, so pay pal will ask the user to put in the price information themselves.
The same problem does not happen if the user is already registered or tries to check out as a guest, the price will be sent over to paypal without any problems.
Any help will be apreciated.
Many Thanks for taking the time.