Reduce both your upload & download bandwidth. Go to LW's menu bar, Tools>Options>Downloads & reduce it to about 90% of your real true speed. Do the same for uploads. Go to Tools>Options>Uploads>Basic.
To find your true speed, do a speed test & choose one from a site near you http://www.t1shopper.com/tools/speedtest/
If the speed is quoted in kbps then divide it by 8 to give you KB/s. (ie: 8 bits = 1 Byte)

If 90% doesn't do the trick then reduce it a little further. You might also want to disable Ultrapeer capabilities. See the option for this under Tools>Options>Speed.