The Fatal error in a protected block means that there was some fatal error in some part of the netlist/models which has been encrypted. Now this may be in the PFD/CP model which is produced by the PLL noise aware flow, because that's protected - or it may be elsewhere in your design models.
The second error is a consequence of the first - not enough data was produced for it to compute the power spectral density plots.
I found one similar problem in our databases, but it was not clear what the solution was - the problem went away, but I couldn't find a record of how it was solved. Anyway, what I'd suggest you do is:
- Try installing the latest (MMSIM72) Hotfix and seeing if the problem goes away. You may need to re-characterize the blocks in case there's a fix in the model produced.
- If that doesn't work, contact Cadence Customer Support at http://support.cadence.com - because it will need detailed investigation with your data. Errors in protected (encrypted) code are necessarily imprecise because otherwise the errors could be used to find information about what's in the encrypted code.