In the same link as shown before ( https://www.virtualbox.org/ticket/11145#comment:8) is the solution to both the Vir... [by danielsender]
That's the thing though, I don't get anything except a Windows message "The program stopped working".
My virtual box is not working since I have upgraded my lion OS.
VT-x is being used by another hypervisor. (VERR_VMX_IN_VMX_ROOT_MODE).
VirtualBox can't operate in VMX root mode. Please close all other virtualization programs. (VERR_VMX_IN_VMX_ROOT_MODE).
So I found a forum thread here : https://www.virtualbox.org/ticket/10965, and the solution seems to install again the virtual box again.