Invalid URI: The URI scheme is not valid. on submit deef Inventory

[TNE-germany]

i try to update the quantity of a item, but always get Invalid URI.
it comes on inventory and price, with same credentials i can get the offers, so the credentials are correct.
its for the german marketplace

var feedID = amazonConnection.Feed.SubmitFeed(xml, FeedType.POST_INVENTORY_AVAILABILITY_DATA);
Anyone has a solution?

[RenzoF]

what are you passing in xml, a path to the XML file or the string contents?
either way, can you try the other way as well to see if it works?