Hi John,
not much help but we are also experiencing a lot of access violations since upgrading to 4.2 and its happening on multiple environments. New code seems to work fine however existing jobs that are having to use caching to disk are failing.
We have experience this issue with group by, sort and lookups that are paged and very frustrated at this point. Funnily enough the quickest solution to fix 99% of the issues is to turn off the statistics options. Other solutions have been to put in a Data_Transfer prior to the group/sort.
I have opened a case with SAP but as per usual we have to wade through the typical questions before getting to the meat of the problem.
Looking at the note posted by Sebastian I'm hoping the fix indicated will be out very soon as we are losing a lot of confidence in the products having also encountered significant bugs in our recent BI 4 upgrades.
Cheers
Glenn