I have seen a lot of issues with EEPROMs (93LCxx and 24C0x) during power-on and power-off sequences. It is reasonably easy to send a write-enable sequence to chips like this. However. I have NEVER seen any such problems on controllers with on-chip flash. Looks like Atmel has some serious problems here. I suggest you contact the local Atmel Field Application engineer for this one or change to OTP parts.


Jesper