Cannot install 64-bit OSs as virtual machines

[jon80]

In a previous post (http://forums.virtualbox.org/viewtopic.php?f=6&t=17355) I noted that the 64 bit version of Win 2008 Server cannot be used as a guest machine. I've noted that this is the case also for Ubuntu Server 9.04 64 bit edition. That's just too bad because it was just the OS for my AMD processor.

Installation of Ubuntu Server 9.04 is a bit sluggish.

Has anyone encountered similar problems?

NOTE: My environment
Host machine runs Win 2008 Server (64-bit) with Hyper-V. I installed Virtual Box because I have some problem configuring the network interface for guest machines.
AMD Athlon 64 x2 4600+ @ 2.40 Ghz
4Gb RAM

[Perryg]

This is just a shot in the dark here, but running a Hypervisor inside of another Hypervisor Usually is not suggested.

[SSCBrian]

Hmmm. I didn't have any problems running Windows Server 2008 x64 in VBox under Vista x64. I didn't know it wasn't supposed to work.

[vbox4me2]

Hmmm. I didn't have any problems running Windows Server 2008 x64 in VBox under Vista x64. I didn't know it wasn't supposed to work.

It depends what has been selected at install time, a custom install usually installs HV.