If this helps, here is where the process seems to go FUBAR. This is a direct quote from one of our customers:

"it brings me to the paypal site and then it tells me all the info like who im
buying it from (MJM Magic) and stuff like that, and then i click pay now and it
re-directs me to the MJM Magic website saying the invalid parimeter.. this never happend before i've ordered from you guys plenty of times."