"I mean about the uP to lose data and code from its internal Flash memory."

As far as the "PSD" part of the uPSD, I have used the PSD (without the 'u' :-); that is, a separate, generic 'u') in a couple of projects and have not heard of any returns due to Flash memory problems, for what it's worth.

But then, I have also used the AT89S8252 without suffering the problems that some have reported.