Hi, its an Iomega Storcenter ix4-200d. I have done some more diggin around and have found the following errors in the /var/log/messages file.....
Jan 25 09:08:48 Hostd: [2011-01-25 09:08:48.749 177E6B90 verbose 'FSVolumeProvider'] RescanVmfs called
Jan 25 09:08:48 vmkernel: 0:17:55:38.288 cpu9:8153)Vol3: 1488: Could not open device 'naa.600508b1001052395359574746470000:6' for probing: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.288 cpu9:8153)Vol3: 608: Could not open device 'naa.600508b1001052395359574746470000:6' for volume open: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.292 cpu9:8153)Vol3: 1488: Could not open device 'naa.600508b1001052395359574746470000:2' for probing: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.292 cpu9:8153)Vol3: 608: Could not open device 'naa.600508b1001052395359574746470000:2' for volume open: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.293 cpu9:8153)FSS: 3702: No FS driver claimed device 'naa.600508b1001052395359574746470000:2': Not supported
Jan 25 09:08:48 vmkernel: 0:17:55:38.293 cpu9:8153)Vol3: 1488: Could not open device 'naa.600508b1001052395359574746470000:5' for probing: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.294 cpu9:8153)Vol3: 608: Could not open device 'naa.600508b1001052395359574746470000:5' for volume open: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.297 cpu9:8153)Vol3: 1488: Could not open device 'naa.600508b1001052395359574746470000:8' for probing: Permission denied
Jan 25 09:08:48 vmkernel: 0:17:55:38.297 cpu9:8153)Vol3: 608: Could not open device 'naa.600508b1001052395359574746470000:8' for volume open: Permission denied
Jan 25 09:08:48 Hostd: [2011-01-25 09:08:48.775 2D233B90 verbose 'Hostsvc:

atastoreSystem'] VmfsUpdate: got VMFS message [N11HostdCommon18VmkernelUpdateVmfsE:0xf5be5a0] timestamp=1295946528775762 specific=0 name= label=
Jan 25 09:08:48 Hostd: [2011-01-25 09:08:48.837 177E6B90 verbose 'FSVolumeProvider'] RefreshVMFSVolumes: refreshed volume, id 4a6da393-781c6277-133e-78e7d1e13754, name datastore1
Jan 25 09:08:48 Hostd: [2011-01-25 09:08:48.837 177E6B90 verbose 'Hostsvc:

atastore'] SetVolume: Datastore 4a6da393-781c6277-133e-78e7d1e13754 has changed provider volume pointer
Jan 25 09:08:48 Hostd: [2011-01-25 09:08:48.837 177E6B90 verbose 'Hostsvc:

atastoreSystem'] ReconcileVMFSDatastores: Done discovering new filesystem volumes.
Jan 25 09:08:48 Hostd: [2011-01-25 09:08:48.837 177E6B90 info 'TaskManager'] Task Completed : haTask-ha-host-vim.host.StorageSystem.rescanVmfs-356 Status success
I have also run some fdisk commands to try and fix as other threads have suggested.