You're either port forwarded OR you're using UPnP. I'm not sure how you can do both at the same time & definitely not have both enabled within LimeWire at the same time. It makes a difference. If you port forwarded then you should set LW to manual port forwarding. If your connection device is set to UPnP enabled, then LW should also be set to UPnP.

I would tend to think from your description of your history that your isp is to blame. Who is your isp (internet service provider)? (ISP's always say they don't block when they do!!! It's PR!!!)

I might suggest to try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.) & then reset your options in LW next time you open it. ie: set LW to manual port forward or UPnP depending upon how your device is set up & enabled.