We upgraded a client to GW 2014 about 8 weeks ago. They since found that around 10% of attachments are unreadable. While most are pdf files, some are excel files. If it is a pdf attachment and I forward that same message and attachment to another client (also using gw14) the attachment opens fine. If I then forward the file back to the original client it then opens fine. I don't have that success with the excel files but it is a current workaround for the pdf files. It is not every attachment and it is a bit random but in all we feel it is around 10%.

Any ideas?