Always getting the 'grub>' line command when booting

Hi there,

I installed Ubuntu Studio 13.10 alongside a preinstalled Windows 8.1 (upgraded from Windows 8 before installing Ubuntu). This is on a recent (2013) TOSHIBA Satellite C870D-121 laptop that can only boot in UEFI mode.
After 3 attempts with boot-repair, all I can is the 'grub>' command line.
The generated boot-repair reports a

• 6715137
• 6715291
• 6715434

The GNU GRUB version is 2.00-19ubuntu2.1
Is there anything else I can try to get this issue fix?
Thanks.