VCB Acquiring Disk Lease for snapshot failed

Hi,

everytime i´ve tried to Backup my vm´s with VCB i get a error message like " Acquiring Disk Lease for snapshot failed". Before this error, seems that it works well (snapshot will be created and removed...).

My Vm´s running on a netapp NFS Share with ESX 3.5 Hosts.

Anyone an idea what´s wrong ??

Thanks

Regards