Can not mount samba with this option "credentials"

[John Wong <johnw@wonghome.net>]

I can not mount the samba server with this option "credentials" a few
days ago.
It can work before, and if i use options "user=myname" and type the
password, it still can work.

My system is amd64/sid,
uname -a: Linux redcat 2.6.32-5-amd64 #1 SMP Tue Jun 1 04:34:03 UTC 2010
x86_64 GNU/Linux

my credentials file have 3 line like this:
username=myname
password=mypassword
workgroup=MYWORKGROUP

my fstab like this:
//sambaserver/share /samba cifs
iocharset=utf8,credentials=/etc/smbmount.conf 0 0

dpkg -l | egrep -i '(smb|samba)'
ii libsmbclient 2:3.4.8~dfsg-1 shared library for communication with
SMB/CIFS servers
ii libwbclient0 2:3.4.8~dfsg-1 Samba winbind client library
ii samba-common 2:3.4.8~dfsg-1 common files used by both the Samba
server and client
ii samba-common-bin 2:3.4.8~dfsg-1 common files used by both the Samba
server and client
ii smbfs 2:4.5-1 Common Internet File System utilities - compatibility
package
ii winbind 2:3.4.8~dfsg-1 Samba nameservice integration server

Please help, and thank you.