I find it hard to believe that UPnP is not working. Are you running any antivirus software on that machine?
Yes, N360. I've tried fiddling with permissions, network trust, etc., including cutting off all antivirus and firewall protection. Still the same.
Are you sure it is not Vuze?
Maybe try another client like µTorrent.
I've tried µTorrent in the past, but for whatever reason, I get that nag screen whenever I add a torrent. The developers couldn't figure out why and refused to drop the nag screen, so I dropped µTorrent. I also like the built-in transcoding engine for my PS3, which brings me to the next thing below.
Since UPnP is all software/firmware and not a single piece hardware it can't be a broken router. I think you should have a look at the client's services (UPnP device host, SSDP service)
I'm beginning to suspect something wrong with this, actually. My PS3 would normally run slower than dirt without UPnP, but I started it up today and it says UPnP is available and I don't experience any lags. That would suggest that UPnP may be fine as far as the firmware is concerned.
Unfortunately, that brings me to my software. I uninstalled Vuze, reinstalled; uninstalled the specific UPnP plugin, reinstalled. I guess it could still theoretically be Vuze, but I'm not sure. Then there's also the actual UPnP services in Windows 7 Home Premium. I've checked them, disabled them, restarted them, set them to automatic, set them to manual, etc. I still get the same results. I've run CHKDSK, sfc /scannow, etc. to see if there's any OS corruption, but they don't turn up anything. I'm running of ideas, guys. There's got to be something I'm overlooking or not trying somewhere down the line. Keep the replies coming. I really appreciate the help.