unlock machine after guest additions execute

[Jobias]

I am working with a virtualized machine.
I execute (via guest additions) a script in my guest linux machine, which in instance creates a background process on it.
The execute process return normally, and the process is running on the guestOS.
I powerOff the machine, but when trying to unlock it, it just keep on that for ever.
I need then to kill the VBoxWebServer to recover control of machine.

LOGIN
16.02.2012 13:42:28: CREATED new session: a1ddfaf915db39f8-0000000000000001
16.02.2012 13:42:28: CREATED virtualBoxMOR: a1ddfaf915db39f8-0000000000000002
16.02.2012 13:42:28: machineMOR created: a1ddfaf915db39f8-0000000000000003
16.02.2012 13:42:28: Console got: a1ddfaf915db39f8-0000000000000004
16.02.2012 13:42:28: Powering Up, the beginning of the problems. VBoxWebService output freezes
16.02.2012 13:42:29: progressMOR for powering Up: a1ddfaf915db39f8-0000000000000005
16.02.2012 13:42:30: Elapsed time to launch VM process: 2025 miliseconds
16.02.2012 13:43:11: /opt/tmp/executeProcess.sh 11
16.02.2012 13:43:12: PID generated: 1120 Work completed: True
16.02.2012 13:43:51: progressMOR for closing VM: a1ddfaf915db39f8-000000000000000b
16.02.2012 13:43:58: Unlocking after switching off
And after killing the VBoxWebServer
16.02.2012 13:45:30: The underlying connection was closed: An unexpected error occurred on a receive.

Any idea?
This does not happen with normal commands or scripts....

Thanks!

[Technologov]

Few developers here.
Better ask dev questions on vbox-dev mailing-list.
https://www.virtualbox.org/wiki/Mailing_lists