Error starting Ubuntu VM on Virtualbox; windows 7

Failed to open a session for the virtual machine OystersVM.

The virtual machine 'OystersVM' has terminated unexpectedly during startup with exit code -2147483645 (0x80000003). More details may be available in 'C:\Users\Nidha\VirtualBox VMs\OystersVM\Logs\VBoxHardening.log'.

Result Code: E_FAIL (0x80004005) Component: MachineWrap Interface: IMachine {85cd948e-a71f-4289-281e-0ca7ad48cd89}