Looking at the xml document it looks like the problem is because this is a non inventory item? Are all the items non-inventoried, the reason I ask is that if they are non-inventoried then you will want to check the IV00105 and see if there is a record in this table with a currency id and currency index. There should be at least one record in this table with a currency id and currency index if you are registered for Multicurrency. If you are not registered for multicurrency there still should be a record in the IV00105 but there would not be a currency id or currency index in the table.
The reason that you need a record in the table is that we check this table to determine if you are registered for Multicurrency or not since we can't check registration in GP this is how we check for Multicurrency.
Please let us know what you find.