I found, with out making other changes to samba config, that I can get QuickBooks 2006 Pro to work in a multi user mode as outlined here:

http://www.quickbooks.com/support/faqs/qb2006/829e206e.html

Note: There simply has to be a user logged on to the server (not QB) that has owner permissions on the .qbw file AND has launched (but doesn't need to be running) QuickBooks in the alternate host mode described above.

Personal Note: Intuit may just like Microsoft a little too much :)