When setting the browsable check box, webmin seems to put in browesable instead of browsable, this causes testparm to fail to understand it. I manually changed it and now testparm is happy, I have samba 3.6.3.
Are you sure "browsable" is the correct option? I have Samba 3.2.11, and the man page says :
This parameter is a synonym for browseable.
This controls whether this share is seen in the list of available
shares in a net view and in the browse list.
Default: browseable = yes