Mac unbootable after install on an USB stick

Hi there!

Sorry about asking another MBR question. I know that the issue of messed up boot information is a theme many others already wrote about, but I cannot figure out which of the previous threads contains the information I need in my case....

Story is, I was installing from a 9.04 Live CD running on a new MacBook running 10.5.8 (booted from CD) and installed Ubuntu on a USB stick plugged into it. I remember that the installer asked where to install the boot loader, and I kept the default, something like harddrive0, and proceeded. I know that this was a mistake when the Mac no longer booted from the harddrive...

The content of the drive still looks fine, the partitions do not have any strange names or flags, it just doesn't boot it anymore... Reinstalled the system (keeping user data) no effect, blessed the System Folder, nothing... "fdisk -u"...

I would be very happy if someone could give me a hint to where to find the right info, maybe even a case just like mine. I would like _my_ Mac back not a clean new one ;)

Thanks a lot!

Stefan