Updated: March 17, 2015
This is going to be a very weird tutorial, today. Namely, we will fix a problem with the Virtualbox startup by using something approaching magic. Indeed, the issue you are facing reads as follows. Recently, you've upgraded your Virtualbox installation to version 4.X or something. Then, all of a sudden, it no longer starts. Instead, it throws an error.
The error message reads something like CERT_E_REVOCATION_FAILURE, and you feel like slitting your wrists. But don't. Let me show you how this kind of problem is debugged properly and smartly, and it will also give you insight into a hundred other, similar phenomena you may encounter. It's also a good lesson in Windows command line.
Virtualbox no longer starts. Can't be any easier than that. There's nothing useful in the Event Viewer logs, and you do not think anything has changed on your system. You think. But apparently, something has, because Virtualbox no longer runs properly. The popup suggests reinstalling Virtualbox, but that's not going to help. We need something else.
The sensible way to resolve this is to think for a few moments. As it turns out, Oracle has tightened the security of Virtualbox, starting with version 4.3.14. This causes lots of Windows users to go crazy with errors. One of these is CERT_E_REVOCATION_FAILURE.
So, we have a hardened program, and it's now complaining about revocation of certificates. Interesting. My gut feeling tells me this is somehow related to the Windows certificate verification process. Specifically, online and offline certificates. Since our Virtualbox is a local installation, we're most likely fighting an issue with the offline verification.
Then, you probably have some kind of a group policy or similar that may have changed the default Windows setup, which used to allow offline approval for commercial certificates. When you have all this tied up, then the fix becomes easier to find.
What we want to do is check - and change if necessary - the default value for certificate approval. This can be done with the tool called SetReg, which is part of the .NET 1.1 SDK. We will download and install the kit and then run the tool, and see whether this fixes the problem. Sounds like magic, does it not.
If you install it on Windows 7 and above, the system may complain, but you can safely ignore the error, especially if you're not running the IIS Web server. Then, fire up cmd as Administrator, navigate to the SDK install path, and run a command.
Based on the MSDN howto, we need:
<path to>\Microsoft.NET\SDK\v1.1\Bin\setreg.exe 5 true
And magic! Virtualbox will run now just fine!
You will probably hate me for saying that fixes are obvious when you know what to look for, how to look for, where and when, and if you have the right dose of technical expertise to pretend to have intuition for difficult problems. But that's the truth, really.
In this case, hopefully, I've tickled you imagination and helped you develop a sense of troubleshooting for seemingly hopeless errors. Certificates, aha, something corporate sounding, it must be group policies or alike, how do we change that, and so forth. That's the kind of healthy thinking you need to fix problems of this kind. Best of all, there's no need to reinstall anything. Just some command line hackery. Enjoy.