VixDiskLib_Open error due to disk lease failure

Hi,

VixDiskLib_Open using SAN is failing with following error:-

diskLibPlugin: [2011-08-15 14:36:50.343 05052 error 'DiskLibPlugin'] Acquiring disk lease for snapshot-12121[XX_Data] ABCCOMXXVM/ABCCOMXXVM.vmdk failed with vmodl.fault.SystemError.

Anybody aware of any possible reasons for this failure?

TiA.