Problems running VBox in AMD64

[maraujo]

I have installed VirtualBox 1.5 in a AMD64 double core (with AMD-V) running Ubuntu Feisty 7.04 64 bits and a 2.6.22 kernel. The installation was successful.
Now when I try to run a Ubuntu 32 bits server in a Virtual Machine it prompts:

"Your CPU does not support long mode. Use a 32 bit distribution"

Could anybody help me to fix this? Why do I have to install a 32 bit distribution? Does VBox get screwed because of having kvm module installed? Is this a bug?

Thanks in advance for your help,
Regards

Miguel