Downloads slowing down could also be because you are maxing out your upstream on an asynchronous speed connection to the internet such as Cable or DSL which causes your computer's acknowledgement of the data it receives to be delayed behind other data it is uploading to other people also using Gnutella. Are you also uploading a lot when doing these downloads? If so, try limiting the upstream speed in LimeWire to around 75 to 80% of what your max upstream speed is according to your ISP. So if you can only upload at 32 kilobytes/sec maximum, limit your upstream to around 20 or 25 kilobytes/sec.