virtualbox.org

I'm running windows 8.1 and I had some trouble after updating virtualbox past version 4.3.12 so I reinstalled 4.3.12 but I see that there have been 2 more releases 4.3.16/18, since 4.3.14 the one that failed.
When I click the check for updates in VBox Manager it says I am running the newest version. Is that because there are still problems with updates on windows 8.1?

Not that I am aware of. I have never had any problems updating VirtualBox on Windows 8.1 .

You can always download from the VirtualBox website and install it yourself. The current version there is 4.3.18 .

In general, if you have problems with VirtualBox, you can delete your current version and install the same one again or a later version. It will not affect any of your vms.

I always uninstall the current version and fresh install the new one if it is a major upgrade eg 3.x to 4.x . I also make sure that the vms are shut down, not saved.