Sounds to me like it is most likely a firewall issue. If you go to school you might want to contact the T1 administrator. But before all of that, make sure that the files you are trying to get, you are not downloading from T3 or higher sources. 99% of those are corrupt files and will cause the exact problems you are mentioning. The best things you can do is try to download from cable users and files that have as many sources as possible. If none of this helps, contact the admin, I faced a similar situation in college with a T1 and adjusments had to be made to the network.