Kernel Panic while VDP backup for RHEL 5 VM

The error i see in logs is

2014-11-11T01:01:32.703-5:00 avvcbimage Warning <0000>: vSphere Task failed (quiesce, snapshot error=35): 'An error occurred while saving the snapshot: Failed to quiesce the virtual machine.'.

2014-11-11T01:01:32.703-5:00 avvcbimage Error <17775>: Snapshot 'VDP-1415685662b72b27a63567b8ab1fd759cb69bb4ac32b03e4fa' creation for VM '[XXX_VMW_LUN12] xxx/xxx.vmx' task creation encountered a quiesce problem

This resulted in kernel panic

Anyone know about this issue, my rhel 6 backups are going fine.

thanks