Error Starting Virtual Machine (was Previously Working)

[freeman00in]

Hi,

I initially installed the VirtualBox-4.3.20-96997-Win in January this year. It was working fine for about a month, the period I was using it.

However, today, after a gap of about 2 months when I again wanted to use it, it refused to open and flashed the error message mentioned below. I read somewhere that reinstalling helps in solving this problem and so I did exactly that by first using the same version and when that didn't work I downloaded the recent version (VirtualBox-4.3.26-98988-Win) and installed it. However it too is displaying the same message now.

Can someone help me in solving this problem?

System OS: Windows Vista SP1
Firewall/Antivirus: Yes (Windows/Avira respectively)
OS to run in VM: Ubuntu

Error Message

    Failed to open a session for the virtual machine CS50 Appliance 2014.

    The virtual machine 'CS50 Appliance 2014' has terminated unexpectedly during startup with exit code 1 (0x1). More details may be available in 'C:\Users\Viper\VirtualBox VMs\CS50 Appliance 2014\Logs\VBoxStartup.log'.

    Result Code: E_FAIL (0x80004005)
    Component: Machine
    Interface: IMachine {480cf695-2d8d-4256-9c7c-cce4184fa048}

Log files attached in zip format.