XP Pro network problem

[lievenv]

Hello,

I have two computers attached to a router. There's also a broadband modem connected to the router. Both my pc's can access the internet. PC1 can access all the shared folders on PC2, but PC2 can't access any on PC1. Both PC's are part of the same workgroup and show up in the workgroup computers list. When I doubleclick PC1s computername on PC2 it get "\\PC1 is not accessible. You might not have permission to use this network resource..."
I ran the network setup wizard several times on both PC's, changed my PC1's computername 3 times (now all 3 computernames and their shares are showing up in my network places of PC1, not on PC2, there only the current PC1 computername is visible, but no shares in PC2 network places). I also checked my firewalls, but they allow all home network traffic.
And everything used to work fine. Dunno what happened...

Any idea's on how to clean up this mess?

Thanks,
V