[root@drivebox ~]# host mothergoose
mothergoose.kittyheaven.net has address 192.168.200.49
mothergoose.kittyheaven.net has IPv6 address 2001:239a:af8:105d::1

[root@drivebox ~]# mount.cifs //mothergoose/storage /mnt/mothergoose -o user=nobody
Password:
mount error(22): Invalid argument
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
[root@drivebox ~]# mount.cifs //mothergoose/storage /mnt/mothergoose -o user=nobody,ip=2001:239a:af8:105d::1
Password:
mount error(22): Invalid argument
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
[root@drivebox ~]# mount.cifs //mothergoose/storage /mnt/mothergoose -o user=nobody,ip=192.168.200.49
Password:
[root@drivebox ~]# mount | grep mothergoose
//mothergoose/storage on /mnt/mothergoose type cifs (rw,mand)
   ^^^ works only if -o ip is set to an ipv4 address

[root@drivebox ~]# uname -a
Linux drivebox.kittyheaven.net 2.6.18-194.8.1.el5 #1 SMP Thu Jul 1 19:07:06 EDT 2010 i686 i686 i386 GNU/Linux
[root@drivebox ~]# rpm -q samba3x-client
samba3x-client-3.3.8-0.52.el5_5