Problem converting 64bit OS VM into Nested ESXi 5

Now I know this is not officialy supported by VMware, but still I need to ask..

I have two nested ESXi 5 Servers running on a physical ESXi 5 Server.

When trying to convert a Windows Server 2008 R2 that resides on the physical server (in other words - V2V), with VMware vCenter Converter Standalone, to the nested ESXi Server, i got the following error:

"The destination does not support 64 bit guest operating systems".

I have searched all over for a solution to this.. But I didn't quite found out what to do to solve this problem.

I don't seem to get what values to change\add in the configuration files etc.

Help?

Thanks in advance,

Martin.