Strange infinite blocking error under network loads

[robertsdotpm]

Under periods of large network congestion and latency the person uploading data will eventually fill up their send buffer, usually only transferring a small amount of data until it errors out with "resource unavailable" - (doing this forever) which indicates it would block. The strange thing is: the receiving side -also- has the same error and only manages to receive a small amount compared to the person uploading (they eventually go out of synch: upload, say 10,000 bytes, download 2000.) So then, what is happening with the data? I almost think it's a network problem but TCP should handle something like this.