Another old email dated 7/3/2009 that I dug up from my sent items:
Once Group Chat was deployed, everything was working except for the file transfers. When an attempt was made to try and send a file, it attempts to transfer with a window popping up and then it fails with the message:
A file transfer error occurred. The underlying connection was closed: An unexpected error occurred on a send.
Searching the web returned the following blog post: http://blogs.technet.com/daveh/archive/2009/03/22/file-transfer-problems-in-ocs-2007-r2-group-chat.aspx
While this blog post seemed relevant, it didn’t fix the problem. After troubleshooting the issue for a bit, we ended up opening IIS Management Console to check the certificate assigned to the website. When we clicked on the “view certificate” button to check the certificate, nothing happened so we went ahead to reassign the same certificate to the website and from then on, the file transfers started working. This was most likely either due to one of the following:
1. The certificate was reissued at some point with the old one deleted which would explain why the “view certificate” button didn’t do anything.
2. There may have been some problems during the install when assigning the certificate.