I might try another NIC in each of the computers. Replace one at a time and retest. And check that crossover cable, another component which can be swapped.
I have a home network of two PCs joined by direct ethernet cable. This works fine 99% of the time, but some files won't copy from one to a shared drive on the other. The copy will start, with network utilisation at 2-3% for a few seconds. Then packets stop flowing, and after between 30 and 120 seconds I get an error, either "The specified network name is no longer available" or "Semaphore timeout period expired". During that time I can ping in either direction, so the network is working, it's just that the file has stopped going anywhere. However Windows Explorer (if I initiated the copy from Explorer) locks up until I dismiss the error dialog. It's not an Explorer problem though; the same thing happens in a batch copy.
There's a definite set of files affected e.g. one is an Excel spreadsheet of about 1.5 Meg. But other much larger files copy fine. And there's no pattern e.g. other spreadsheets are OK, it's not all the files in one folder etc.
I'm running Windows XP Home Service Pack 1 on both PCs, and they're both up to date with Windows Updates. I'm using manual IP addresses at both ends. I have ZoneAlarm (a freeware firewall program), and it's configured to let all traffic through to the IP addresses. I've even changed the drive mappings to use IP addresses instead of share names, in case it was a DNS problem, but that didn't help either. I've set both network adapters to use 100 MBits Full Duplex. The adapters are "SiS 900-Based PCI Fast Ethernet" and "Macronix MX98715-Based Ethernet".
So I'm at a bit of a loss, and wondering if anyone can shed any light. Thanks in advance.