Just curious if anyone has any ideas why I can't remote into PC's within my subnet behind my router since installing the 26 kernel on my new ASUS RT-N16? I could do it before with my old WRT54GS and now I can't anymore.
The only commonality is the gateway. Set your pc's ip addresses manually with no gateway, if they are in the same subnet the packets will find the other pc via the broadcast .255 in the subnet, connect to the other pc via ip address not name, if this works, then you can blame the router, and the dhcp packet is somehow being mangled and/or the gateway (router) is somehow dropping the packets. Check the router logs for that info.

I set the static IP of my HTPC (host machine I'm trying to remote into) to 192.168.1.140/24 with no gateway IP. I'm using a laptop with an IP of 192.168.1.125 (handed out by DHCP) as the client. Still didn't work.
I can swap the ASUS for my old Linksys (running original Tomato 1.28) and it works like a charm. It's almost like there's a setting that's not allowing the RDP to work.
The laptop on DHCP is still sending it's packets to the gateway for retun to the HTPC, but you have proven the router is a sorce of the fault by swapping, so my previous suggestion was a waste of time probably. If the router is not on, no router present, using a switch, does the problem still occur?
I've not ran into this, and it really doesn't make much sense, as a router controls WAN, not LAN traffic. There are no settings to contol pc to pc broadcast. The only thing I could suggest is trying a different mac address for the LAN ports on the router as this does sound like a hardware layer issue. A intelligent switch could control such traffic but that has not been mentioned here.

Well…..it ended up being a Windows 7 firewall constraint. I checked out all the firewall rules associated with RDC and the public rule for port 3389 was not turned on. After flipping that switch, all is well. Not sure why the older firmware worked without that rule being initiated but….oh well. It's working now….thanks for the help….