I've found a work-around. You can mount your share with the "-t cifs" option instead of "-t smbfs". I have the same problem with gentoo (kernel 2.6.7, samba 3.0.4-r1) and debian (testing, kernel 2.6.4, samba 3.0.2a).
Hope for a solutions.
(you can also look here: http://bugs.gentoo.org/show_bug.cgi?id=49749 )