VirtualBox: Eating up 100% CPU, freezing Windows 7

[Hartmann, O.]

I discover that when running Windows 7 in a VirtualBox On FreeBSD 10
(r238968: Wed Aug 1 14:26:40 CEST 2012), VBox is most recent from the
ports, that the VirtualBox eats up 100% CPU time and freezes Windows 7
for more than a minute. For a minute or so, I can work, then, the freeze
occurs again.

I can't see this behaviour with a Ubuntu Guest on the same box. Is there
Windows 7 specifica to be aware of?

Regards,

Oliver