VBox hangs after first reboot of machine

[Kicer]

Hi

I was trying to install 64 bit machine for the first time. Windows 8.1. Installation process went well untill reboot: Windows said it would reboot now, but nothing happend.
VBox window was responing (menus etc) so was the Windows (I could move mouse, but screen was empty). However nothing happend. I've reset machine manually and it hanged on window "starting virtual machine 0%". I've removed whole machine and I've repeated process - the same.

Then I've tried newest ubuntu (also 64bit). Similar situation, but the first reboot was fine. Second one killed the machine.
I've a few 32bit machines and all are working fine for a few months.

Any suggestions?

[Kicer]

It seems that the problem was in my btrfs filesystem. When I moved disk images to another partition I had no problems.