virtualbox.org

Hello,
today I worked with my Ubuntu64 guest without any problem, saved the state of the OS and closed the vm.
Everything was fine but now it didn't start anymore.
This is the first error window:
After clicking "Abort", the loading bar disappears and this second error window shows:
The logfile is attached.
My host is Windows7 64bit.
Googling doesn't seem to be helpful, I tried to delete the saved state and restart guest OS. Later I upgraded to 4.3.20, which is my current version. Unfortunately got the same error everytime.

Can anybody help me?

Remove KB3004394.

For more info, check the following thread.
'Windows 4.3.20 specifically for errors due to security'

Thank you, you're right it was the same problem! Now it works!