I decided to open a new thread for my issue, as of my problem seems to be caused by another issue as is discussed in the thread I posted originally to: http://forums.virtualbox.org/viewtopic.php?f=15&t=42726&
I made a photo of the error message (sorry for bad quality) which occurs after halt of my machine: http://i56.tinypic.com/s18fh4.jpg
This occurs if I want to shutdown my machine. The same seems to happen during suspend.
If I change the default stop runlevels in /etc/init.d/vboxdrv from "1" to "0 1 6" machine shuts down properly again! What's the reason for not using the defaults here?
Regarding suspend/resume, if I add "vboxnetadp vboxnetflt vboxpci vboxdrv" to /etc/pm/config.d/module machine suspends/resumes properly again!
Those issues appeared with 4.1.0 Beta1 for the first time, until 4.0.10 powering off and suspending my machine worked without issues.
If you need further information, please ask.