Error 0x80070035, Can't Access Any Shares

So over the past few days, I've painstakingly setup a new Sandy Bridge PC just the way I like it and was preparing to transplant it into my existing system when I discovered I can't access any network shares! It worked fine when it was a completely clean install with just the driver loaded.

System A: DIY Sandy Bridge PC with Windows 7 x64 SP1.
System B: DIY Athlon 64 X2 PC with Windows 7 x86.
System C: Gateway Notebook with Windows 7 x86.

All systems are using MSE for AV, have the firewall and password protected sharing OFF. Network discovery, file and printer sharing, and public folder sharing are on. A gives me error code 0x80070035 (network path not found) when I try to acceses any shares on the network, even its own. A only sees B on the network, not C. B and C can access all shares, inlcuding A's shares. All the systems can ping each other. I thought perhaps when I was setting up A that I disabled a service or feature that caused this, but I've set everything back to way it was and it still doesn't work. I've also tried a second NIC.