I have win 8.1 and Ubuntu 13.10 installed, both are working fine but.. When coming from win-8 and rebooting the PC I will get an "Error: no boot disk has been detected or the disk has failed".
I then have to go in to BIOS and change the start sequence to "Ubuntu" and it will stay that way until next time I use win-8.
If I reboot from Ubuntu it works just fine, I end up in the GRUB and can choose whatever I want to do.
Very annoying and probably (hopefully) easy to solve, but I can't see how.