mauror You probably ran out of space because you started pulling graphical dependencies. The virtual disk is small, you do need to expand it and then expand the FS in the VM. I wanted you to do a quick test in that VM so we'd be testing the same VM.
Anyway I did find the bug in that kernel module, my patch was committed and is already in the ports. That module though has other issues that would require deeper understanding (and possibly full module rewrite). But at least now system doesn't crash randomly.
If you install VirtualBox from ports my patch is already included there, you don't need to apply anything. You just need to upgrade the package. I'm not sure how often the binary packages get updated, I use them seldom.