VirtualBox 5.2.0 has recently been released, which you can read about here.
I decided to throw caution to the wind and install it on my Windows 7 PC at work. The installation went fine and an existing Oracle Linux 7.4 VM started and worked OK. When I tried to update the guest additions it failed to build, but the VM was still working without some of the stuff you need the GA for, like video drivers and shared folders etc. Next I tried an existing Fedora 26 VM. It also started fine, but the guest additions failed with the same error. Timo Hann said it was working fine for him on Windows 10, so I figured it was a Windows 7 issue and forgot about it.
I got home and tried on macOS Sierra. Same error. After a bit of Googling I couldn’t find a solution, so I raised a ticket. That was subsequently closed as a duplicate from an issue (#17163) first raised in 5.2 RC1. So far no fix. See Update.
For reference, 5.2 seems to be working fine for me for existing VMs, provided I don’t try to upgrade the guest additions. It does mean I’m pretty screwed for new VMs that require guest additions for shared folders, as I’ve not got guest additions installed on any new VM, on Windows 7 or macOS hosts.
At this point I’m going to try and stick with 5.2, rather than backing it out, and see how it goes. 🙂
Update: There is a revised version of the guest additions (5.2.1) which you can download separately from downloads page. Download that ISO and use that rather than the default guest additions and it solved my issues on my Win7 host. Got to try on my Mac when I get home. Thanks folks! 🙂
Update 2: The 5.2.1 guest additions also solved this problem for me on Oracle Linux 7.4 and macOS Sierra hosts running OL7.4 guests.