Custom desktop computer cannot download files

Hello. I have built my own computer (GA-880GM-UD2H Motherboard, AMD Phenom II 3.4GHz CPU, 16GB RAM), and I also own a laptop. Recently, whenever I try to download any file from Google Chrome or Mozilla Firefox, they seem to come in really small chunks of MBs. After a while, and a pathetic percentage, the download stops claiming errors. When I restart it, it simply resumes for some more MBs, and then stops again. The laptop has no issues. Where should I start looking for a problem? What could the problem be?
