Comment 46 for bug 420933

OK, the problem is gone for me but unfortunately I can't exactly tell why. Thats what I did.

(see my harddisk/partition configuration in my prevoius post)

I reinstalled grup on /dev/sdb with `sudo dpkg-reconfigure grub-pc` like Felix suggested.
-> same problem.

I checked /dev/sda in Palimpsest an it was marked as bootable. I removed the bootable flag an REBOOTED (didn't switch power of!).
-> same problem

I SHUTDOWN the pc an removed /dev/sda (IDE drive)
-> problem was gone

I put /dev/sda back in again
-> problem still gone

My guess is, that the system hadn't recognized the removal of the "bootable"-flag after the reboot, but after powering off the system on powering it back on again.