I'm having trouble uploading videos to DropBox.

I'm having many difficulties uploading my videos to dropbox from itunes. All I do is publish my video to iTunes from iMovie. Then, I drag the video from iTunes, and put it in my dropbox folder. They're mostly only 4 minute videos, or smaller. But, when I upload it to DropBox, it takes almost two days, IF it even uploads without quiting on me. Whereas, on my Parents iMac, it only takes at - the most - 3 hours. We have wireless internet, and that's what both of our computers are on. I even hooked our computer up to the wifi box (for lack of better words... considering I have absolutely no idea what 'the box' is called. 🙂 Oops...) and it would do nothing. I have no idea what to do, and these videos are important. I do one a week. And they have to be uploaded before friday, each week.