I also disabled UPnP for the same reasons, although I found out only after I downgraded the FW to 2.01 (I had problems with 2.05, which is the latest for hardware B1, SE Asia).
Edit: This I can't explain.
I found another site that can check for vulnerabilities:
http://upnp-check.rapid7.com/
and the router passed, i.e., no response to a discovery request.
I decided to enable UPnP and try again, and it passed. I went to GRC Shields Up, and it passed.
I booted the modem, router (with UPnP enabled), and PC, and tried again in both sites, and the router passed.