I forgot to mention that I found an ERRATA on "mask set errata for mask 3M05C", particularly "MCGV1 Can Cause a Very Short Clock Pulse" paragraph, SE128C-MCGV1.
It seems to me that the problem descripted is the same I experience this days.
However I would to be really sure that this is the same problem I have, because I'm using the mask 2M05C (older ?!) and not the 3M05C, and of course that it will be solved in the final mask.
I
f the problem has been already solved, I would know in which mask the fix was introduced, in way to request from Freescale a sample of the corrected chip, to be sure that I have no other problem to solve for the final production.