Cannot delete a vmdk file from datastore in the GUI or using CLI, getting an "invalid argument" error

Hi,

I cannot delete a vmdk file from my datastore. The file in question (S9_1-flat.vmdk) cannot be deleted using the vSphere Client or using CLI. I've attached the output from my SSH session:

/vmfs/volumes/50bb5d47-5677d7b4-cb59-90b11c1479d7/S9 # ls -al

drwxr-xr-x    1 root     root          3640 Aug 17 15:45 .

drwxr-xr-t    1 root     root          1540 Aug 17 14:59 ..

-rw-r--r--    1 root     root            27 Jul 10 09:15 S9-365b1e05.hlog

-rw-------    1 root     root     17179869184 Aug 17 15:45 S9-365b1e05.vswp

-rw-------    1 root     root     107374182400 Aug 18 11:56 S9-flat.vmdk

-rw-------    1 root     root          8684 Aug 17 15:46 S9.nvram

-rw-------    1 root     root           491 Aug 17 15:45 S9.vmdk

-rw-r--r--    1 root     root             0 Mar 21  2014 S9.vmsd

-rw-------    1 root     root          4172 Aug 17 15:45 S9.vmx

-rw-------    1 root     root             0 Aug 17 15:45 S9.vmx.lck

-rw-r--r--    1 root     root          3033 Aug 17 15:39 S9.vmxf

-rw-------    1 root     root          4068 Aug 17 15:45 S9.vmx~

-rwxrwxrwx    1 root     root     1099511627776 Jun 29 10:07 S9_1-flat.vmdk

-rw-------    1 root     root     586263035904 Aug 18 11:01 S9_2-flat.vmdk

-rw-------    1 root     root           520 Aug 17 15:45 S9_2.vmdk

-rw-------    1 root     root       8561355 Aug 15 19:44 vmmcores-1.gz

-rw-------    1 root     root       3581220 Aug 16 07:52 vmmcores-2.gz

-rw-------    1 root     root       2968111 Aug 16 07:53 vmmcores-3.gz

-rw-r--r--    1 root     root        227605 Aug 17 14:54 vmware-79.log

-rw-r--r--    1 root     root        227281 Aug 17 15:02 vmware-80.log

-rw-r--r--    1 root     root        232708 Aug 17 15:16 vmware-81.log

-rw-r--r--    1 root     root        226958 Aug 17 15:28 vmware-82.log

-rw-r--r--    1 root     root        235389 Aug 17 15:35 vmware-83.log

-rw-r--r--    1 root     root        230933 Aug 17 15:38 vmware-84.log

-rw-r--r--    1 root     root        236001 Aug 18 09:18 vmware.log

-rw-------    1 root     root      97517568 Aug 17 15:45 vmx-S9-911941125-1.vswp

/vmfs/volumes/50bb5d47-5677d7b4-cb59-90b11c1479d7/S9 # rm -f S9_1-flat.vmdk

rm: can't remove 'S9_1-flat.vmdk': Invalid argument

(Note that the permissions on the file are currently set as 777 as I initially thought that this could be a permissions issue).

Another thing to add is that the "S9_1.vmdk" file has gone missing, and if I attempt to create a new Hard Disk in Settings I get the message "S9_1.vmdk already exists". What is the best way to remove "S9_1.vmdk" that seems to be hidden, and also remove "S9_1-flat.vmdk"? Will I have to delete the entire datastore?

Any assistance would be much appreciated.