mount error(12): Cannot allocate memory

Do you have the following situation:

• You’ve got a share on Windows (XP, Vista, 7) that you’re trying to access from a Linux system, in this case Ubuntu.
• Mounted through /etc/fstab or directly through the command line.
• Initially, it works great, but then loses the mountpoint – you’ll go to, say, /mnt/server/mountpoint but there are no directory contents. “mount” shows the path as still mounted.
• umount’ing the directory and then trying to remount it provides this gem of a message:

  mount error(12): Cannot allocate memory
  Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

Of course, since you’re probably a reasonable system administrator, you go and check the memory allotment. top looks fine and nothing else on the system is complaining.
The solution, kindly provided by Alan LaMielle’s blog, gives a registry fix on the Windows side of things. In case that link ever breaks, here is the summary of what needs to happen on the Windows system:

• In HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management, set the LargeSystemCache key to 1 (hex).
• In HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters, set the Size key to 3 (hex).’
• Restart the “Server” service and its dependencies (on my Windows 7 box, these were “Computer Browser” and “Homegroup Listener”, and I had to restart the service twice for the dependencies to also come back up.) Alternatively you can just restart the Windows system as you’re probably due for a large set of updates anyway.

Then re-run the mount command (for entries defined in /etc/fstab, use sudo mount -a) and your shares should be restored to their former glory.