Hi Bill,
I recommend checking the install notes in this doc ftp://exftpp.symantec.com/pub/support/products/NetBackup_Enterprise_Server/320793.pdf
It has some differences from the standard Exchange Admin guide for 6.5.
Also, when you run your tests be sure to disable Granular backups. If you search the forums or look in my post history you'll see what i mean.
Here is also a really good post for setting up for GRT backups by Mouse:
https://www-secure.symantec.com/connect/articles/netbackup-granular-recovery-technology-tips-and-caveats
As for your error specifically -
Did you install from the newish 6.5.4 x64 install? I can't remember the issues there but you may want to try installing from it instead, if you havent already.
Good luck,
Matt