Sometimes failing drives get stuck and freeze the OS when they are attached to an ATA bus (internal desktop or laptop). One trick i've used a few times is insert the drive in a firewire case like this hint.

Transfer your data (usually a finder copy). When or if it fails (mechanical or intermittent power), cycle the power!. This will reset the drive state and throw up a firewire alert in the Finder (about disconnected disk).

Once the drive spins back up and registers with the OS again, you can usually find that the finder will continue the copy after the interruption. It might thow up an error saying a file could not be copied (note filename for later), but it can still proceed with other files. Your mileage may very, but i have succesfully retrieve potentially lost data this way for an entire 80gb drive. Cooling or orientation were of no help in that situation.

Of course, professional services are more reliable, but more expensive as well.

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dirtymouse - 'fix a troubled Mac' - troubleshooting PDF book