On 4.2.18 r88781 (the About says r88780), I'm getting corrupt graphics in a Win8 x86 guest on a Win8 x64 host. The moment Guest Additions are installed, no text is drawn, no bitmaps, just solid color empty squares/shapes (I saw a tray notification's round balloon). There are other symptoms as well. Disabling 3D acceleration in the host VirtualBox solves it. It looks like this:
A
blog post here suggests it works okay with some older versions, and that it may depend on settings.
Is there a known workaround that does allow acceleration to work?
By the way, a warning message in the Guest Additions installer could help.

I was about to give up and reinstall the guest OS, but I finally found that disabling 3D acceleration helps.