Corrupt PDF files

Hi 

We have a shared folder which four computer access that open and save files to the shared drive.

We recently updated to the most recent firmware 6.10.2 and since then whenever someone trys to save a PDF attachment into the job folder, it will open a few time before displaying the error "pdf either not a supported file type or because the file has been damaged"

We have tried savind the PDF locally onto the users desktop, and the file opens everytime, but when the file is moved from the desktop into the shared folder the same issue happens.

Any suggestions?