MacBook internal HD "disappeared"

[iamback]

I started up my MacBook this afternoon, planning to install a bunch of stuff to make it into a "real" development machine.

I immediately got message there were software updates, including a security update, which I thought was a good idea. Reality was a bit different.

I unchecked QuickTime and iTunes (neither of which I want anyway), and let it rip with the rest; when it got to the last step, installing the security update, it took ages... it showing "optimizing system performance" and basically never completed. Everything else I clicked got me a spinning beachball. In desperation, I closed the lid, hoping I'd shock it into waking up - the HD light remained on. I opened the lid again - no change. So I turned off the power: there was literally nothing else I could do!

Then I tried to reboot again, the disk light came on briefly and then went out. Start up sound ... then nothing for a long while ... then a blinking folder with a question mark inside instead of the grey apple. At that point I connected my external HD (which has a bootable clone, albeit an old one): its light came on immediately, there was disk activity ... and the machine booted from the clone. The three partitions of the external HD could be seen, the internal HD was nowhere. Disk Utility didn't show anything more, nor did /Volumes.

I also tried to boot from the install DVD - same result: no internal HD to be seen. It's as if it's dissolved into thin air.

Now what? I'm out of ideas.