Sounds more like a hub or cable issue than a computer problem to me.
With such a small network, I'd test each computer with a direct X-cable connection to eliminate the hub and current cabling.
If problems continue at BOTH stations, and your SME has 2 network cards, switch the local & global configuration, so you can eliminate the current local card.
IF you have a card with a realtek 8139 chipset, you may want to search the forum for comments about that card and issues invovling it.
Hope this helps
Mike