So a few weeks ago, I made the switch from Windows 8 to Ubuntu 13.04.
Whenever I tried to boot my computer, the cursor in the top left corner would flash a couple times, then I'd get a screen saying "No bootable device insert boot disc and press any key".
Somehow, I managed to "fix" the problem using a combination of Boot Repair and something else (I don't remember what that something was). If I let my computer boot normally I'd still get the error, but if I brought up a menu to pick a device, I had the option of "ubuntu" as well as my hard drive and various paraphanalia, so I left it at that.
Fast forward to a couple of days ago, I decided to upgrade to 13.10, and now I'm back to square one. I still get that error message if my computer is left to boot on its own, and the option to choose ubuntu in the boot device menu is no longer there.
Here, have a pastebin: