First of all, let's thank Steif for putting a lot of effort with many people at the moment. Idon't know if any of this will help but here goes:
1) it would seem that if the host from which you are d/loading is busy, then that slows things down.
2) if the host is a modem connection, then that certainly slows things down regardless of your connection.
3) if the host goes offline and shuts down the PC, then you PC has to find another host to d/load from. That could take ages.
4) if your a modem user, save what you spend on your phone calls and buy a faster service. I never d/load from a modem and found a way to stop modems uploading from me. They slow down everyone else. Sorry, but that's fact.