Just upgraded the kernel on my VirtualBox image of OEL6 and the VirtualBox Additions failed to build. The problem was that the latest OEL6 kernel is now kernel-uek.
$ uname -a
Linux soavbox.oracle.com 2.6.32-200.20.1.el6uek.x86_64 #1 SMP Fri Oct 7 01:50:00 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux
This seems to confuse the dkms rebuild of VBox Additions. See Virtual Box Ticket #9332 clipboard support broken – OEL 5.6, OEL 6.1.
To fix it I followed the suggestions in the ticket above:
Voila now my OEL 6.1 works great with VirtualBox again!