Up until April 2007 Shopsite 8.2 (and 8.0) had successfully processed orders from such countries as Norway and Denmark which include characters such as ø, æ, å etc. in the names or addresses.
However since we installed 8.3 on 4/24/07 we have had two failed orders, one from Denmark and one from Norway. Both failed orders included a ø character. The Payment Processing Error that the customers got after submit is as follows:
Error: SGS-020003: Invalid XML
Replacing the ø character with a o caused the order to complete successfully. I'm thinking you broke something in the 8.3 release because we've had no problems with orders which include the letter ø or other Scandinavian characters up until then.