When I download a file, it usually takes longer than when I'm downloading 2 files at the same time. So let's say I'm downloading The 7th Guest, & on another site I'm downloading an update to MacOs X...it goes faster for them to finish than if I'm just downloading one. Like 50 minutes difference. That seem odd to anyone?

Short answer, that SHOULDN'T happen... Its possible your ISP sees multiple open connections and increases the bandwidth allocated to you, but that seems highly irregular.