Secondary VMs cannot power ON, after rebooting a host.

Here is my configuration:

2x hosts (R710)

2x VMs

1x vCenter

Running ESX 4.0 U2

If I restart any of two hosts, the VMs move to another host. When the restarted host comes back, the secondary VMs stay on "Power OFF" under State column.

If I Turn FT off on one of the VM, the other secondary VM will automatically power ON. Once that secondary VM is ON, I went to turn FT back ON again, then the secondary VM is created with power ON.

How can I fix this problem?

Thanks in advance for your help.

Johnny