Error occurs while trying to start VMs "VMX can't operate in root mode"

Binary package hint: virtualbox-ose

OS: Ubuntu 9.10 x86

(using full disk encryption with guided LVM mode)

Error Details{

Result Code:
NS_ERROR_FAILURE (0x80004005)
Component:
Console
Interface:
IConsole {0a51994b-cbc6-4686-94eb-d4e4023280e2}

}

ProblemType: Bug
Architecture: i386
Date: Mon Nov 16 07:19:39 2009
DistroRelease: Ubuntu 9.10
NonfreeKernelModules: nvidia
Package: virtualbox-ose-qt 3.0.8-dfsg-1ubuntu1
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: virtualbox-ose
Uname: Linux 2.6.31-14-generic i686
VirtualBoxOse.DpkgList:
 ii virtualbox-ose 3.0.8-dfsg-1ubuntu1 x86 virtualization solution - base binaries
 ii virtualbox-ose-qt 3.0.8-dfsg-1ubuntu1 x86 virtualization solution - Qt based user
 ii virtualbox-ose-source 3.0.8-dfsg-1ubuntu1 x86 virtualization solution - kernel module