Dual head - black screen on Ubuntu 13.10 guest on 4.3 only

[Studzinek]

Hi I will post whole story:

Host: i7-930, X58A-UD3R, 8GB RAM, GT240 with proprietary driver v319, Stock Ubuntu 12.04 x64 (Unity 2D)
Guest: Stock Ubuntu 13.10 x64

Story:
On VirtualBox 4.2.18
1. I created VM with one screen and 3d support
2. I installed u13.10, update/dist-upgrade, installed vbox addons
3. after reboot all works great
4. I changed to dual screen in VM settings. After that I get normal login screen but after login Unity wasn't visible, only right mouse click shows menu (I was able to get into System Preferences through right click -> change desktop background) but panels wasn't visible.
5. I powered off VM, switched back to one screen, and boot up. After installing CompizConfig and disabling FBO in OpenGL settings I can boot normally with two screens and everything works great:) so FBO was an issue with damaged Unity with two VM screens.

Today I upgraded do 4.3. After that I can't get VM with dual screen working. I tried create new u13.10 VM and install VM system from scratch. After installing vbox addons VM works great (with animations and 3d support) but with only one screen. When I added second screen I get black screens after login (loggin screens are normal). I tried disabling FBO and other options in OpenGL section with CompizConfig but I can't get it working.
I had to downgrade to 4.2.18 to get it working again. Now everything works as before (on 4.2.18).

How can I solve my problem with Unity 3D and dual screen in 4.3?

I attach two logs from 4.2.18 and 4.3 (logs are long because there are restarts to change monitor count and other experiments with CompizConfig/OpenGL settings)

Sorry for my bad English.

[Nath]

I have the same/similar issue. I just upgraded from 4.2.x to 4.3 on a Win 7 host. I had been running Ubuntu 12.04 inside a guest with dual monitor setup. Everything worked ok with the windows maximised to each monitor with 4.2.x. However, after upgrading, the windows are fine until I pass the login screen. At this point, the windows don't seem to fit the size of the monitors correctly when they are maximised and the screen go black. I have had to drop to a single monitor

[Kacey]

I am also having the same issue, it is not hardware related as I get this on my work PC, and my home laptops. Anyone found a workaround?