Lost Workgroup access

I have two PCs connecting to a DSL router through a D-Link DI-614+ router.
They're both connected to it be Cat 5 cable. The one PC can see the workgroup
just fine, but the other can't. I've reset the configurations in Network
Places, I've checked everything else suggested here, but the one PC still
won't see the workgroup. Both machines are using the latest version of Zone
Alarm and are configured identically. I only want to share a couple folders
on each machine.
The local net used to work just fine. Suggestions?
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I know enuff to be dangerous.