Sudden crash of VirtualBox.exe
It happens from time to time that the running Virtual Machine suddenly crashes, without any particular action on the guest system other than using it normally.
For example, last time I was just about to enter a search term into the address bar of the Firefox Browser of my Ubuntu 14.04LTE guest system when it crashed. The moment I clicked on the address bar, VirtualBox crashed. This was only one example of many crashes.
Unfortunately, the appearing error message doesn't say much (see attached screenshot) and from the log file I couldn't find an answer either. It looks like it didn't log anything.
I can confirm that I have the same behavior and it happens around 3 times a day.