WB3.9 requires KS3.1 and to enable the memory on the ACA with KS3.1, you need to run ACAtune. You should also use ACAtune to maprom KS3.1 for extra speed. And yes, it is a free download so there is no reason not to use it.
The reason you are getting a guru is most likely due to the scsi.device that comes with WB3.9 does not work with CF cards. Check this FAQ:
http://eab.abime.net/showthread.php?t=61666 'OS 3.9 Boing Bag 2 issue'