There's a heap of info about how to set up your LW for best performance in the thread below.
Configuring LW for best performance

You'll need to do a speed test & find out your download/upload speed in KB/s. You can do a speed test here (scroll down the page to find more test sites for other countries). Then follow the advice in the thread above for how to set up your LW.
http://www.dslreports.com/speedtest?more=1

If I were you, I'd call your ISP (painful I know) & ask if they've started using traffic shaping for p2p apps. If you were getting 80 KB/s (I know you said kbps but I'm guessing you meant KB/s as that's how LW measures speed) before then such a sudden drop just sounds very suss.