Mac will not see Win 7 PC on Network

Recently installed a Mac with Snow Leopard for a client. At that time the Mac could see the PC and vice-versa. NOW, the Win 7 PC can see the Mac, but the Mac can't see the PC. All other PCs and the other Mac on the network can see his machine. He can see them all except for the Win 7 machine.

I have tried some quick fixes, but to no avail. The version of Snow Leopard is 10.6.6 and the PC is running Win 7.

This just started all of the sudden. Any help would be appreciated. Also, there are NO HARDWARE ISSUES on either machine

These are a pitr. If it's got any sort of software firewall (especially McAfee) on the Win 7 box, I'd start there first.

Pretty sure it's not a firewall. This just started out of the blue.

It was working fine for 6 months prior.

May not be it in your case, but I can tell you it just started out of the blue here also. I mention it because the McAfee firewall (and Norton also) will do exactly what you are describing. Dealt with it for over a year off and on before I finally convinced the boss to put in a hardware firewall here and turn that stupid thing off.

I've had users click Don't Allow on a popup window and that firewall would block access to his computer on the network. And it might only affect one other computer, half or all - it made no sense. Sometimes it would be an update to McAfee itself that caused it.

Microsoft firewall being enabled can hide the pc from the rest of the network.

Will check the Windows Firewall, but i'm almost positive it's off.

Any other ideas out there ??

Windows Firewall is OFF and the ony other program concerning the network is Avast.

I still can't get the Mac to see the Win 7 rig. However, I can see the Mac from the Win 7 PC just fine.

Any other assistance would be greatly appreciated.

BTW, their other Mac, running Leopard 10.5.8, can see the Win 7 rig just fine. Could it be an issue with an update with Snow Leopard ?
Maybe something I could shut off or adjust ?

Thanks in advance for any assistance.