GRUB rescue error: no such device

Hi,

I seem to have got into a problem.

The current status is that I have to have the RW-DVD that I installed from in the drive. If I do then I get to choose from the "Boot from Hard Disk", INSTALLATION" etc. menu - the "Boot from Hard Disk then gives the correct choice of OS.
If I do not have the installation DVD in the drive then I get:

error : no such device : nnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnn.
grub rescue >

This is a dual boot of Windows 7 with Linux. openSuSE replaced Ubuntu 13.04 and after that replacement I got the above situation. I did not knowingly change any boot options during the initial installation.

Since then I have tried changing options in the boot loader section of YAST, and have reinstalled. No progress.

Any ideas or pointer welcome!