Recompiling VirtualBox kernel module

I have used VirtualBox 2.1.0 on openSUSE 11.0 without problem.Two days ago, I updated the openSUSE kernel and the VBox no longer works. When lauching it, I get the following messages:

1.-
Virtual machine ‘FreeDOS’ has terminated unexpectedly during startup.
Code de résultat :
NS_ERROR_FAILURE (0x80004005)
Composant :
Machine
Interface :
IMachine {ea6fb7ea-1993-4642-b113-f29eb39e0df0}

2.-
The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Re-setup the kernel module by executing

‘/etc/init.d/vboxdrv setup’

as root. Users of Ubuntu or Fedora should install the DKMS package at first. This package keeps track of Linux kernel changes and recompiles the vboxdrv kernel module if necessary.
Virtual machine ‘FreeDOS’ has terminated unexpectedly during startup.

Code de résultat :
NS_ERROR_FAILURE (0x80004005)
Composant :
Machine
Interface :
IMachine {ea6fb7ea-1993-4642-b113-f29eb39e0df0}

3.-
I have run the following command:
P-2:/home/pian # /etc/init.d/vboxdrv setup
Stopping VirtualBox kernel module done
Recompiling VirtualBox kernel module failed
(Look at /var/log/vbox-install.log to find out what went wrong)

4.- And in the file vbox-install.log:
Makefile:170: *** Error: unable to find the include directory for your current Linux kernel. Specify KERN_INCL=<directory> and run Make again. Stop.

As I am relatively new to linux, I never compiled anything, can you tell me what I have to do to correct the point 4.

Using YaST, install make, gcc, and kernel-source. Then redo the step

/etc/init.d/vboxdrv setup

Thank you for your help.
make and gcc were already installed, I had to install only kernel-source. And the recompilation was done yet without problem. Now my VirtualBox is again functionnning correctly.
Thank you again for your help.