I have a ESXi 5.0 installed and when I am Installing Ubuntu Server 12.04 LTS (32 bit) it is giving an error saying grub installation failed?

Please check the below screenshot of the error.

1. I have other Ubuntu servers running fine on this esxi server, so I don't think problem is with ESXi.
   
2. I have 32 GB of ram spare on this ESXi and have given 2 GB of RAM to this 12.0 LTS VM.
3. I have given 2 cores of processor.
4. I have tried supplying different ISO Image to this VM as I thought the 1st image that I downloaded has errors.. But defiantly that's not the case as all 3 different ISO images that I downloaded of Ubuntu server 12.04 LTS (32-bit) can't be corrupt!!
5. Just to make sure that the Image does not have problem I used that Image to install it for testing on stand alone system. it works fine there!!
6. This is a production ESXi server with which I can't play with, how ever I can play whith the Ubuntu Server 12.04 LTS (32-Bit) VM that we have created on that ESXi.
   

I need help on this as soon as possible. go live date of this server is really close.

(This Question is already there on Super user and Server Fault.)