When you say "nothing" gets uploaded... do you mean even when the file passes validation?
That definitely would be strange. I have been able to run server validation with no problem. Is there a chance that the code has been changed at all... like maybe a field in your form does not match up with the validation name.
The other thing to do is to check if it the validation code itself causing the problem... to do this I would put the validation code before the Digital File Pro Upload but then create a redirect on fail to see if it something getting stuck in validation.