I don't really know what Ubuntu is honestly, but i'm pretty well versed in computers so I can offer a tip. Generally when i'm having certain download issues the first thing I try is opening a different web explorer. For example, I am using Google Chrome and I get hit with an apparent dead link or something that just won't function properly I open up Firefox or Internet Explorer and try to accomplish the same task. Nine times out of ten this resolves any issues I have similar to what you are experiencing.
Hope this helps in some way, i'm gonna go Google and see what Ubuntu is now.
*Update*
So i'm not as oblivious as I thought, I just didn't know Ubuntu was a branch off of the Linux operating system. I know what Linux is, perhaps I should google things before I post replies because now i'm not entirely sure my advice will help you in the slightest.