Major scare with MacBook today.

OK, as I mentioned in the last post, I got over the problem with the Ubiquity installer crashing during the Ubuntu install.
What I didn't mention was that when I went to reboot, I just got a white screen -- nothing else -- no Apple or Linux logos.
I really though I had lost yet another HDD on this machine which would be the third in less than a year.
Then I found that I could use the Ubuntu LiveCD to get something to show up -- so it wasn't the graphics card which I had also suspected.
Strangely, though, I was able to mount all of the Linux partitions that I tried as well as the OSX partition. Also, I could read, copy any of the files from these partitions and even play music on the OSX partition.
So, this didn't suggest that the hdd was unreadable.
Then I tried the OSX Leopard install DVD which also booted fine. Here I tried the disk utility and it said the OSX disk verified OK.
I was lost and thought I'd have to bring my Mac to the repair shop tomorrow.
However, as the OSX disk utility didn't show either /dev/sda1 (EFI) or /dev/sda3 (Foresight /), I thought I'd try Parted Magic to see how these partitions looked.
Well, they all showed up but every single one had a yellow warning sign against it.
Just by chance I noticed that the Foresight / partition had a boot flag so I took this out and all partitions lost the warning sign.
Tried again to boot and this time absolutely everything was back to normal.
This is quite incredible as I'm totally sure that boot flag had been there for a while without causing any problems at all. So, why did a simple install of Ubuntu II (alpha3) cause this to turn very nasty? I really do not understand this. Nevertheless, I really was on the verge of making another trip to the Apple repair shop in my city and I'm very glad I didn't have to.

I should mention as well that the Ubuntu II install also seems to mess up the GPT/MBT synchronisation so that you get a "no bootable disk" message when you try to boot (at least into Linux -- not sure if this also happens if you try to boot to OSX). However, this is very easy to fix: In the opening rEFIt page, just move to "Start Sync Tool" and say "y" to the sync suggestion offered.

Incidentally, during the various desperate attempts I made to get this thing to boot, I restored the Mac Darwin boatloader to the MBR. Here's how this is done.
Boy that was scary but had a happy ending.