Try running the 4.x client and you should be OK.
The issue with ReflectionX is that we use a SHIM adapter within the IP stack of the PC, and this adapter is what gets assigned the VPN IP address when you bring up your tunnel. The underlying Windows OS doesn't know anything abut this IP address though (do an "ipconfig /all" and you won't see it anywhere). ReflectionX and various other programs include the actual IP address of the PC in the data portion of their packets, but this IP address is the physical IP address in Windows, not the new negotiated address over the VPN. Reflection basically tries to create windows on the wrong IP address and it doesn't work.
In the VPN client 4 we changed the adapter the client uses so that the underlying OS can now see it, similarly to a dialup PPP connection. Do an "ipconfig /all" with the 4.0 VPN client and you'll see the extra adapter in there along with it's actual IP address. ReflectionX should use this IP address automatically and everything should work fine.
