As a test try d/loading a file from here:
http://www.magnetmix.com/audio2.shtml.
You should get pretty fast d/load speeds. If you don't, that may mean your isp has started throttling p2p apps. You could call them and ask, though they might not say. Could be they only do it during peak hours, so try d/loading at different times of the day.
Could also be related to your firewall. You'd need to post your system details:
System details - help us to help you.
See this thread also:
Connection problems? Check here first!