I was doing a little experimentation earlier and put the drive from my titanium pb (40gig, 5400 rpm) into my Pismo. It booted up and ran fine, no problem. I turned it off to mount it in the bracket though, and it came up with the flashing question mark. Booting from a CD and running drive utility, the computer sees the drive but is simply not mounting it. Unfortunately you don't have the option to mount it either. now the same problem is happening when I put the drive back into the titanium too.
It mounts fine when installed into an external USB 2.0 case, but as soon as it goes into one of these powerbooks, becomes unmountable. I need my hard drive back, so I could really use some help here.
When you put the drive in the external case, did you run Disk First Aid on it? Possible your OS X install got goofed.
If you did, and that didn't help, try this:
1. Put the drive back into the external case.
2. Connect it to a Mac running OS X.
3. Pull a disk image of the drive, preferably at the block level.
4. Run a scan of the disk image to convert it to an ASR image.
5. Format the external drive.
6. Clone the disk image to the external drive with ASR.
If that doesn't work, then your OS is hosed.