Download of Ubuntu fails

Solution 1:

Use torrents to download the file. I've experienced several random pauses while downloading large files.

Or, you can use download managers (like DAP - Download Accelerator Plus, IDM - Internet Download Manager, etc.)

Solution 2:

You may have more success downloading via BitTorrent. You'll need a BitTorrent client (I have had success with uTorrent in the past), and you can download the torrent file appropriate for your CPU here; you'll most likely want the ubuntu-12.04-desktop-amd64.iso.torrent for a 64 bit system and ubuntu-12.04-desktop-i386.iso.torrent for 32 bit.