VMware: operating system not found after upgrade to 5.5

I am testing the vmware native driver of nova compute component.

My environment should be workable before I upgrade my vCenter and EXSi from 5.0 to 5.5.
After the upgrade, I found all the existing VMs boot from nova can not be started in my vCenter with 'Operating system not found' error.

I tried to delete the image cache in my datastore under the _base directory and try to boot a new one, it doesn't help, the problem is still.

I get a new image from here: http://partnerweb.vmware.com/programs/vmdkimage/debian-2.6.32-i686.vmdk , this one is workable in my env.

So, I am confusing what's wrong with my existing image which should be workable fine before my upgrade.

Here is my image in the glance:
[root@openstack-vmware-nativedriver-test2 ~]# glance image-show b919aaae-9347-4d31-ba0c-8bcb137b00c4
+-------------------------------+--------------------------------------+
| Property | Value |
+-------------------------------+--------------------------------------+
| Property 'vmware_adaptertype' | ide |
| Property 'vmware_ostype' | rhel6_64Guest |
| checksum | 6cb76a2cb41c7950829d901c3c7b34d1 |
| container_format | bare |
| created_at | 2014-03-03T14:15:25 |
| deleted | False |
| disk_format | vmdk |
| id | b919aaae-9347-4d31-ba0c-8bcb137b00c4 |
| is_public | True |
| min_disk | 0 |
| min_ram | 0 |
| name | rhel65-x64 |
| owner | 6109ca03531d4dbebd1f7364cf6032e4 |
| protected | False |
| size | 2590703616 |
| status | active |
| updated_at | 2014-03-03T14:15:42 |
+-------------------------------+--------------------------------------+

[root@openstack-vmware-nativedriver-test2 ~]# head -20 rhel65_cinit_dev.vmdk
KDMV
��

�

# Disk DescriptorFile
version=1
CID=530d8ad5
parentCID=ffffffff
createType="monolithicSparse"

# Extent description
RW 62914560 SPARSE "rhel65_cinit_dev.vmdk"

# The Disk Data Base
#DDB

ddb.virtualHWVersion = "4"
ddb.geometry.cylinders = "62415"
ddb.geometry.heads = "16"
ddb.geometry.sectors = "63"
ddb.adapterType = "ide"