samba - Jan 2010 - Samba write bits being set incorrectly on FreeBSD 7.2

I've found that read-only files become writable when copied from Windows 
XP to my Samba 3.3.3 mount on FreeBSD 7.2.
   I have the "map archive = no" option.  If I change this option to
"yes" then the write bits are cleared (and execute bits set), as 
expected.  Shouldn't the read-only permissions be maintained regardless 
of the map archive option?
I've never seen this on Linux version of Samba.  Could it be ext3
vs. ufs?

Thanks,
Mark Lokowich
Compellent Technologies