Bluewhite4,
I think I should have mentioned one thing about the upgrade process. After each upgrade you need to run the DBTest utility on it to fix an issues that are fixable at that point. Also keep an eye out for Referential Integrity errors since that is a major source of DB corruption.
As for the issue with whether or not your machine is 64 bit that shouldn't make a difference, but then again I never ran the software on a 64 bit machine yet. The .NET issue I ran into before when I loaded software versions and then had to delete them to load previous versions, but that hasn't happened since they started unbundling the DB software from the SAaD software. It could mean that your version of .NET is not the correct one, try reloading the latest version of the SAaD application to see if it repairs it.
Thanks,
TE