I suspect this is a rather unhelpful error generated which is trying to say "that file is too large".
Currently there's a limit of 20MB for uploaded files. I guess you're probably hitting this?
I realise this 20MB could be quite restrictive in the case of uploading a Zipfile of lots of things, so could look at increasing it. But for now you could try making it smaller and seeing if that helps?
Joe - Voice Admin