I had 5.2.20 installed and mostly have 32-bit Windows VMs running under Windows 10 Pro 64-bit OS but I do have one 64-bit OS (running MS-SQL so I wanted access to more RAM).
Yesterday I installed 5.2.22.
My 32-bit VMs started but not my one 64-bit VM (Windows 2012 64-bit OS). The error was that the guest was reporting was "Attempting to load a 64-bit application failed." The file referenced was "\windows\system32\boot\winload.exe" with Status: 0xc000035a.
With huge apologies to the engineers to help out on the forums, I started to go through the FAQ that they direct people to when a 64-bit guest option is not available in VM (which, in this case, those options were no longer available) - but I stopped. It occurred to me that the only change was that I had upgraded my VirtualBox version.
I decided to drop back down to 5.2.20. The 64-bit guest started with no problems.
So my environment was already configured and allowed for 64-bit guests and something that 5.2.22 introduced did not like my laptop's environment.
I'm happy to produce a log next weekend when I feel safer about 'breaking' my environment but I wanted to at least offer up my experience for others who experience the 'loss of 64-bit functionality' with 5.2.22.