when trying to import a purchase order I forgot to create the entries in the pricelist before starting. Thus the header was created but now lines where added. The result window showed the number of errors but the lines didn't have a message. Trying again after creating the pricelist again failed, because the header was created and committed. I then could delete the header, but it is even worse, if only some of the lines couldn't be added.
I'll going to created a patch to show the errormessages.
I think it should be possible to run the import again then, without deleting the header. Either by not committing the header (and eventually lines which didn't fail) or by allowing to add lines to an order which is not committed. Even better might be, to import an order completely or not and marking at least the first failing line with an error message.