If you enable all of the UPnP options in the mIRC Options/Connect/Options/Port dialog and then enable Identd (turn off "enable only when connecting") and then use PortForward to check the UPnP settings on the router, does port 113 appear in the UPnP ports list? Is your External IP (as displayed by PortForward) correct?
No, the port 113 doesn't appear in the list, and I even tried rebooting mIRC.
Yes the external IP displayed is correct.
Note that I tried to /socklisten -p test 8002 right after, and it correctly appeared in the list.
This is on win7 pro 64bits, the test on winXP was wrong, the router used doesn't have upnp.