"No signature for our key list"

[Sebastian Silva]

Hi James and OLPC,
I know you might be able to help to figure out why suddently my XOs 1.5 
refuse to flash my OOB built images.
All I get is "No signature for our key list". However, by the same 
process, images built for XO1 seem to work fine.
Security is even disabled on these XO1.5s and fs-update in ok prompt 
doesn't seem to do anything.
How can I verify what went wrong? I could not find anything suspicious 
in OOB output.

Thanks in advance for your help
Sebastian