I am having the same problem with everything i try downloading.
No it is not my ISP, everything worked fine up till 2 versions ago. I use limewire pro which i purchased from the limewire site.
My firewall isn't the problem as it was fine before.

My system is:
AMD Athlon 3000+XP
1024MB ram
Biostar Motherboard
Windows XP Home Edition
120gig hard-drive
Radeon X800GTO Video Card