I believe your problem is hardware related, not software related. (By the way: It can't be related to the shipping lock, as that can only engage the carriage when the carriage is all of the way to the top of the scanner. Trust me on this one, as I've had my 3200 apart.)
You might try looking over in the Yahoo! Groups Epson 3200 group for information. Should you decide that you're desperate enough to disassemble the scanner, there are instructions there (relating to how to clean the underside of the glass) that show you how to take the scanner apart.
If you decide that this scanner is dead and you don't want to shell out the money for a new 4780, Epson is selling refurbished 3200's through the Clearance section of their web site for $299. No bargain, but not as bad as the new scanners either.
Best of luck to you.