At System Preferences > Startup Disk I select a disk with Mac OS X (10.5 or 10.6) installed, but when I click Restart I get this error message:
You can’t change the startup disk to the selected disk. The bless tool was unable to set the current boot disk.
I have 10.6 installed on an internal hard drive and 10.5 on an external drive.
I have completely erased both disks from Disk Utility; done Verify Disk, Repair Disk, Verify Disk Permissions, Repair Disk Permissions; reinstalled Mac OS several times on both drives...
Looks like something is wrong with internal hdd. I have tried to restart the machine in target disk mode, but I got
You can't start up with target disk mode. The nvram tool was unable to set a preference