Those are possible causes, but I don't think the issue is network-related. I don't have a wireless card in my desktop and I'm able to copy (and synch using a command-line program) to the share in about 10 seconds. It seems to get caught up in the CRC checking part of the process - which it does whether or not I select the CRC option.
Any other thoughts? The transfer status box predicts it will take more than 4,000 hours to finish the synchronization. I don't really have that much time...