RE: Synchronize All Ownership & Security brings up an error about CD835... user is not found
I actually figured it out (a lot of time later). I had both SL 2011 and SL 6.5 databases on the same server (as described above.) In one of the processes (still not sure which one) several triggers were added to acct_xref, acctsub_xref, etc. tables in the 6.5 system DB that were connected to the newer 2011 databases. I still am not sure if I selected something wrong or if there was an error in one of the scripts that I ran but long story short, the system was looking for the user CD835... to run the triggers and that user did not exist. Once I deleted the triggers (they were obviously incorrect) everything was good.
At the end of the day I'm not sure what caused it (which is what scares me the most), but after the change I am able to run both versions without issue. Sounds like you may have had the same issue and the restore prior to the triggers getting created fixed it (just a thought)