PC is not accessible

I recently changed ISPs, and in the process decided to upgrade my router as I have been wanting a gigabit one. Well everything went fine, set up all my PCs as required (needed to forward a few ports for a few applications). Somehow though I have encountered a problem.

I have two Windows 7 Ultimate x64 PCs, which I have networked together. I am able to login with a remote desktop connection just fine, I am able to access the homegroup section fine too. But the section under "Network" doesn't work. Well it works in that I can see PC1 and PC2, but if I click on the remote PC. I get the error:

\\PD-PC is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions.
The remote procedure call failed and did not execute.

They are on the same router and subnet, and wired if it matters. They are actually the only two things plugged into it, all other PCs use the FiOS provided router. My router is the D-Link DGL4100. No third party firewalls, just the Windows one (and the router one). Prior to the change in routers, everything worked fine.

I have searched around the internet, and almost every thread I go to seems to have a different "fix" for this, none have worked for me. I am stumped. I am sorry if I have forgotten to provide you with some information that would help

i take it UPNP is enabled on the router? the only thing i can think of if they work fine on another router.

Yes I do have UPNP enabled.

Thanks for the response.

able to ping through IP and or name to see if it goes through the routers DNS. by sounds of it with all drivers up to date, ur gonna have to contact router manuf

Checking with the router setup page I have a new funny thing that is happeneing.

According to the router, I only have two things connected to it. My current PC (PDi7) and a wireless router. Both are connected, but so is my other desktop (which would be named PD). I am able to ping it fine, with both 192.168.0.114 and PD-PC with no dropped packets or latency. Odd thing is everything is fine still, internet still works fine on it. I am able to transfer files between the PCs. Streaming works. I can still login with a remote desktop connection.

Something else I recently noticed. I have most of my music on the remote PC, as that is essentially what I use it for a NAS and an HTPC at times. So I have my media player setup (foobar2000) to recognize the remote drives. It works, but if I try and "open containing folder" for a file that would be on a remote drive nothing happens. If a file is on a local drive, that option works.

So maybe this is a router issue. I will try D-Link and see what they say.

Thanks again for your time and patience. :)