Hi, I'm having the same problem, but it still doesn't work even after I cranked up the memory all the way (128MB) and enabled 3d acceleration.
inxi -Gx reveals:
Graphics: Card: InnoTek Systemberatung VirtualBox Graphics Adapter bus-ID: 00:02.0
X.Org 1.10.4 driver N/A Resolution 1920x968@60.0hz
GLX Renderer N/A GLX Version N/A Direct Rendering N/A
No driver?
Also I tried running cinnamon --replace, and it loaded but it was unusably slow.
It said something like:
Xlib: extension "NV-GLX" missing on display ":1.0"
I am going to install a new copy of linux mint, with the settings right from the start and see if that makes a difference. My experience with linux has been perpetually fraught with graphics driver problems.
I have a non-virtual copy installed and I'm pretty sure I got the GNOME 3 interface after
uninstalling the nvidia driver, when it didn't work before or after I installed it. It should be noted that the install disk could not boot on my dear new lappy, so I took the hard drive out of it and installed with another computer, and moved it back, then it worked.