samba - Jan 2005 - Permission problem

I have a share mounted using smbfs, rw
 
I can access the share just fine.
 
I can create files on it and modify them all I like.  But if I create the
file using windows, I can no longer modify it. 
 
i.e. I open the share on a windows box and make a directory
then
mv testdir testdir2
 
mv: cannot move `testdir' to `testdir2': Permission denied
 
This is causing me a huuuuge headache right now... does anyone know what's
going on?