I am running Ubuntu 11.10 with Unity. I installed XEN and booted its kernel. The machine booted normally. However, when I started Unity (3D), there were no window decorations.
I tried Unity 2D and the window decorations are present there. I then decided to remove the driver (installed through Additional Drivers) and install it manually like this:
IGNORE_XEN_PRESENCE=y CC="gcc -DNV_VMAP_4_PRESENT -DNV_SIGNAL_STRUCT_RLIM" ./NVIDIA*
...but the window decorations were still missing in Unity 3D. The window decorations are there when I boot the regular Ubuntu kernel (without XEN support).
What could be the problem and how to fix it?