samba - Dec 2007 - Changed UID - CIFS mount now failing with error 13

Hi everyone,

In work there is a windows backup server, and I use a backup script
almost every day to copy some files there.
Everything was working great with the following line in the script for
months now:

        sudo mount -t cifs //homer/backup /mnt/backup-o
workgroup=xxxx,credentials=xxx.txt

Now, yesterday I changed my user uid on the box, from 501 to 500
because nfs was not working for me.
After doing this, cifs mount has stopped working.  I cant be sure if
the two events are related so I thought I would ask here.
I changed my uid back to 501 again, still no joy.

Heres what happens now:

   [root@smpeg1 alastair]# mount.cifs -V
   mount.cifs version: 1.10
   [root@smpeg1 alastair]# uname -r
   2.6.17-1.2142_FC4
   [root@smpeg1 alastair]#


   [alastair@smpeg1 ~]$ sudo mount -t cifs //homer/backup /mnt/backup
-o workgroup=xxxx,credentials=xxx_credentials.txt --verbose
   parsing options: rw,workgroup=xxx,credentials=xxx_credentials.txt

   mount.cifs kernel mount options
unc=//homer\backup,ip=xxx.xxx.xx.170,user=xxxx,pass=xxxx,ver=1,rw,workgroup=xxx,credentials=xxx_credentials.txt
   mount error 13 = Permission denied
   Refer to the mount.cifs(8) manual page (e.g.man mount.cifs)

So can anyone give me a hand?  Is the UID thing totally bogus?

Best regards and thanks,

Alastair