Can't install Ubuntu

[stefan70nl]

I have several VirtualBoxes:
- XP
- Win7
- Win8

And in the past as well Ubuntu.

For some strange reason it stopped working. Installing a new VirtualMachine isn't working: it won't start the installation process. (see below)

Any suggestions?

Stefan

============================
Win 7 SP1
VirtualBox 4.2.2
- New
- 512MB
- New virtual harddrive
- VDI
- Dynamic
- 8 GB
- Start
- Attach an ISO (12.04.1 (86), 12.4 (86 and 64) ..all tried, same result)
- for a brief moment purple screen (with 2 icons at the bottom), then black screen ...the end