I had fully working 64bit Ubuntu 14.04 under VirtualBox 4.3.20. I then updated ubuntu and virtualbox and now I can login but the Unity will not display because compiz crashes with segmentation fault - I have only background without any UI. It seems to be something related to opengl.
Starting Unity from terminal:
stop: Unknown job: unity-panel-service
compiz (core) - Info: Loading plugin: core
compiz (core) - Info: Starting plugin: core
start: Unknown job: unity-panel-service
compiz (core) - Info: Loading plugin: ccp
compiz (core) - Info: Starting plugin: ccp
compiz (core) - Info: Loading plugin: composite
compiz (core) - Info: Starting plugin: composite
compiz (core) - Info: Loading plugin: opengl
compiz (core) - Info: Unity is not supported by your hardware. Enabling software rendering instead (slow).
compiz (core) - Info: Starting plugin: opengl
No available targets are compatible with this -march, see -version for the available targets.Segmentation fault (core dumped)
It seems to be something corrupted in my installation because Ubuntu 14.04 live CD booted from the same virtualbox works without any problems.
Removing the intel driver PPA and force downgrading all mesa packages using standard repositories fixes the compiz crash.
The problem is in the latest MESA 10.3 drivers that came with last update of the intel graphic drivers through PPA. I installed Ubuntu to run both natively and inside VirtualBox. The MESA drivers from intel work in native mode but cause crash in swrast_dri.so within compiz.