Suddenly Failed to open a session 4.3.20/Can't clean unins

[Microbio]

This is really depressing! I am only a user. I read all the threads I can find, but haven't seen a solution.
I uploaded the screen snaps, but not sure you can see it.

It worked fine till yesterday. But today "Failed to open a session for the virtual machine Ubuntu32bit14.04.1."

What's more: when I tried to repair it, "Fatal error" occured, after which the virtualbox.exe even disappeared!

I tried removing everything, including files in C:\Windows\System32\drivers\, and folders in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\. And re-installed the software. But errors still exist.

I just cannot revert it back to the status of yesterday!!!

Host is Windows 7 SP1.

Can anyone help me out!

Anything else I need to upload?

P.s. I read threads such as viewtopic.php?f=6&t=63556&start=180#p300962
but cannot find a solution.

The virtual machine 'Ubuntu32bit14.04.1' has terminated unexpectedly during startup with exit code 1 (0x1). More details may be available in 'C:\Users\ \VirtualBox VMs\Ubuntu32bit14.04.1\Logs\VBoxStartup.log'.

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

[socratis]

Did you update your Windows host? Read the thread Windows 4.3.20 specifically for errors due to security from the post that I linked onwards. It seems that there is an update (KB3004394) that triggers a similar error to yours. See if it fixes it.

[Microbio]

Did you update your Windows host? Read the thread
Windows 4.3.20 specifically for errors due to security from the post that I linked onwards. It seems that there is an update (KB3004394) that triggers a similar error to yours. See if it fixes it.

Thank you @socratis! It does work. It seems now I have to disable the windows automatic update to avoid such unexpected problems.
Microsoft just wasted my whole day!