Firewall blocking traffic, asymmetric routing
Going to hop in here and say that I'm getting the same drops for RDP traffic from my LAN to my office LAN by way of asynchronous routing/VPN (I have static routes on my pfSense redirecting requests to my office LAN to a Linux box I have running PPTP/iptables forwarding. DD-WRT never had an issue with this, but getting frequent disconnects now that I'm using pfSense at home.
Split into its own topic, please don't hijack threads. You need the option to bypass filtering for same interface traffic under System>Advanced.