Our work network has a broadband router at it's outermost part serving a LAN
with addresses 192.168.0.x There is also another router with address
192.168.0.53 serving a subnet 192.168.2.x My work pc is on 192.168.2.99

I have forwarded port 33891 through the main router to the 2nd router and
from there I have forwarded it again to my desktop. My desktop is configured
for 33891 as the listening port.

I can connect from home to the desktop but only get a blank window. Doing
the exact same procedure but with vnc also connects but get a blank screen.

Any ideas? Connecting from the 192.168.0.x network to my desktop works fine,
it's just the double port forwarding which seems to mess things up.