I suppose it's possible they have a different flash chip in there, but every other chip they've used has accepted the same unlock codes...
Hi again all - thread still alive...
...I finally got my Keg out of the car and just performed open heart surgery on it.
The good news 
It
is using a different flash. It's a Silicon Storage Technology SST39VF200A.
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I've added it to the Hardware_FAQ
http://wiki.phathack.com/Hardware_FAQThe bad news 
according to the datasheet
http://www.sst.com/downloads/datasheet/S71117.pdf it looks to me like it should respond to one of the combos i tried earlier...
/dos/backup/debugw 0x5555=0xAA >> /dos/log/PatchAddress.log 2>&1
/dos/backup/debugw 0x2AAA=0x55 >> /dos/log/PatchAddress.log 2>&1
/dos/backup/debugw 0x5555=0x90 >> /dos/log/PatchAddress.log 2>&1
/dos/backup/debugr 0x0 >> /dos/log/PatchAddress.log 2>&1
Could one of you pros check out the datasheet and see if my untrained verdict is correct?
Any other ideas?