API Element Errors

Tried to create a purchase order via the API, for some reason missed the date out so an error was thrown back at me.

However, it was in a different format to the usual errors:

Invalid receipt date ()|

And that’s it - no XML formatting.
For reference, the submission number is 558935c03a1f9

Edit
Just playing about with the available commands. I’ve just tried GetAccountDetails through the sandbox. Literally the only thing changed was a submission number, and it’s returned:

<Error>4The element 'Header' in namespace 'http://www.QuickFile.co.uk' has invalid child element 'SubmissionNumber' in namespace 'http://www.QuickFile.co.uk'. List of possible elements expected: 'http://www.QuickFile.co.uk:TestMode'.</Error>
</Errors>

I will pass this on to our API dev, as I mentioned before these new methods aren’t officially live and do need some further scrutiny. The person who needs to look at this is back on 5th July, so I’m afraid we probably won’t be able to respond before this. That said the first one doesn’t look critical.

I’m not sure about the second error, although it looks like a schema validation failure, did you mix up the order of the nodes? It mentions that it was expecting TestMode?