We have an SFTP (FileZilla) server running and a hundred or so clients connect nightly and upload files in the 20-100MB file range. However, there are 1 or 2 that appear to be able to connect, upload the entire file, then the client reports a failure (winsock 10038 error). The file was actually successfully uploaded. I wrote a simple FTP testing client and it appears that small files (10MB) work just fine. Once we get to around 20MB it starts to fail. I tried bumping up the timeout on the client but that doesn't appear to do anything except increase the amount of time it takes before it reports the failure.
We had them reset their router and test from a few machines at their site and the problem appears on all the machines (so it doesn't appear to be related to the machine). We also checked to make sure they weren't running any anti-virus/firewall software.
To make things even weirder, it occasionally is successful - they're able to upload the file and it completes successfully.
Again, the client connects successfully, can upload the entire file successfully, then it fails.
They appear to be running a Netgear router (don't have the model # yet).
Any ideas on what might be causing this?