I'm not really sure if the return just won't transmit or it is going to sail off without the pdfs.  If it won't convert, you could try disabling the little error checker thingy but I'm not convinced it wouldn't still leave the attachment behind.  I hate to say it, but you might want to give support a call.  You might want to keep your lucky rabbit's foot handy to help your odds of getting someone that knows what they are talking about at support.