Title: cifs_mount_debug_notes 
Subject: Steps to debug mounting a windows share

Search for cifs kernel module
  find /lib/modules/ -name "cifs*"
  uname -a

Load module
  modprobe cifs

Verify kernel module is loaded
  grep cif /proc/filesystems

	nodev   cifs

Try to mount:
  mount -t cifs -o iocharset=utf8,username='DOMAIN.COM\USERNAME' //SERVER.DOMAIN.COM/MYSHARE smb_MYSHARE  

	mount: wrong fs type, bad option, bad superblock on //fa.DOMAIN.COM/DataMart,
	       missing codepage or helper program, or other error
	       In some cases useful info is found in syslog - try
	       dmesg | tail  or so

  dmesg

 	CIFS VFS: cifs_mount failed w/return code = -22
   
Turn on debugging and try mount again
  echo 1 >/proc/fs/cifs/cifsFYI      
  mount -t cifs -o iocharset=utf8,username='DOMAIN.COM\USERNAME' //SERVER.DOMAIN.COM/MYSHARE smb_MYSHARE  

	mount: wrong fs type, bad option, bad superblock on //fa.DOMAIN.COM/DataMart,
	       missing codepage or helper program, or other error
	       In some cases useful info is found in syslog - try
	       dmesg | tail  or so

  dmesg
  
 	 fs/cifs/cifsfs.c: Devname: //fa.DOMAIN.COM/DataMart flags: 0
 	 fs/cifs/connect.c: CIFS VFS: in cifs_mount as Xid: 4 with uid: 0
 	 fs/cifs/connect.c: Username: DOMAIN.COM\USERNAME
 	 fs/cifs/connect.c: CIFS VFS: leaving cifs_mount (xid = 4) rc = -97
 	 CIFS VFS: cifs_mount failed w/return code = -22


echo 0 > /proc/fs/cifs/LinuxExtensionsEnabled  


Look at all the settings:
  for i in `find /proc/fs/cifs/ -type f -print`; do echo '';   echo $i;   cat $i; done

	 /proc/fs/cifs/LookupCacheEnabled
	 1

	 /proc/fs/cifs/SecurityFlags
	 0x7

	 /proc/fs/cifs/MultiuserMount
	 0

	 /proc/fs/cifs/LinuxExtensionsEnabled
	 1

	 /proc/fs/cifs/Experimental
	 0

	 /proc/fs/cifs/OplockEnabled
	 1

	 /proc/fs/cifs/traceSMB
	 0

	 /proc/fs/cifs/cifsFYI
	 1

	 /proc/fs/cifs/DebugData
	 Display Internal CIFS Data Structures for Debugging
	 ---------------------------------------------------
	 CIFS Version 1.48
	 Active VFS Requests: 0
	 Servers:
	 Shares:

In the end I discovered you must also emerge mount-cifs in gentoo:

   emerge net-fs/mount-cifs