Hello there,
When the drive that a dynamic vdi is located on runs out of space while a VM is running, this will crash the OS/2 host. VirtualBox (the Qt version) just sits there and cannot be killed. Even CAD won't work and you have to press the reset button.
If this happens, data loss is extremely likely to occur. I've lost the vdi of the currently running machine twice and the vdi of another machine once.
Judging from what I've heard, this won't happen on Windows and Linux hosts because there is some kind of error handling for these conditions. It would be extremely great if somebody could add it for OS/2.