I'm running Synchronize It 3.5 (3.5.1698) on a Windows 2003 server. I'm doing a sync between the local machine and an ftp site. Sometimes the sync would fail with an error of "An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full". I did some poking around on the net and found a cause of this was too many handles.
I ran Synchronize it and watched the number of handles in Task Manager (view->Select Columns - click "Handle Count". I found the handle usage keeps growing and growing. On the sync I was having trouble the number of handles used by wndsync.exe climbed to 7,990. The number of handles used by "System" was over 21,000. After closing Synchronize It the number of system handles dropped to around 2,000. It seems Synchronize It is opening a file, connection, or something and forgetting to close the handle.
I do have compare set to "content". That might be a clue.