I tried to install Tumbleweed 64bit netinstall on a VirtualBox VM. The very
default settings were used everywhere.

The install process went fine, but after the initial reboot, it fails to start
X. It seems to make several tries and then falls back to the character console.

If I remove the package 'virtualbox-guest-x11', then the graphical login screen
appears, but in very low resolution (maybe 640x480).

The host OS is openSUSE 13.2, and I tried this with both VirtualBox version
4.3.30 and 5.0.5. 

I set severity to 'critical' as majority of users will probably try out
Tumbleweed on VirtualBox first - then chances are they dismiss it forever after
this experience.