Looking at your stream at: Tri-County Public Safety Live Scanner Audio Feed
Something is causing your stream to constantly re-buffer (as you mentioned). However it instantly buffers to 100% but it does this over and over. The instant buffer to 100% is interesting, hopefully someone will have an answer to this.
Compare that to this stream: Thurston County Fire, EMS, and Law Enforcement Live Scanner Audio Feed
Here you will notice the constant scroll of the station description without the buffering.
I would suspect the router or the ISP but you can check the bandwidth on the PC as well.
Bring up TaskManager ( CTRL-ALT-DELETE ) and select Task Manager
Now click on the "Network" tab and see what the network bandwidth at the PC is doing,
Did you get the same re-buffering when you took the router out of the picture?
Is your High Speed Modem in bridge mode? (where the static IP is passed through to your router) or are you double NATing. ie: Your modem gets an IP from the ISP, then it hands out a new IP to your router then your router hands out a new IP to the PC?
If you are double NATing, you might surf around and look for instructions for putting your High Speed Modem in bridge mode to avoid the double NAT situation.
I'm just tossing out ideas here, hoping that something will ring a bell with you so you can get this resolved.