Звиняйте, мужики (и девушки тоже ;-) ).. Ну не помануалил сразу. :] там всё русским языком по белому нарисовано.
Changes to MS-DFS Root Share Behavior
=====================================
Please be aware that the initial value for the "msdfs root" share
parameter was changed in the 3.0.25 release series and that this
option is now disabled by default. Windows clients frequently require
a reboot in order to clear any cached information about MS-DFS
root shares on a server and you may experience failures accessing
file services on Samba 3.0.25 servers until the client reboot
is performed. Alternately, you may explicitly re-enable the
parameter in smb.conf. Please refer to the smb.conf(5) man page
for more details.
http://www.samba.org/samba/history/samba-3.0.25a.html