Hmm, I guess I have to answer myself here, since I solved it. Maybe someone has the same problem. I installed Slackware 10, downloaded the newest kernel sources from
www.kernel.org. Then I compiled the kernel, being sure to incluse all needed hardware, and I added the LSM Kernel patch from ;
http://sourceforge.net/projects/realtime-lsm/
Be sure to enable the security settings like so;
CONFIG_MODULES=y
CONFIG_SECURITY=y
CONFIG_SECURITY_CAPABILITIES=m
CONFIG_SECURITY_SELINUX=y
Read the Readme file for the LSM module and you'll be fine. It's very easy compiling the kernel.
Configure LILO to work with your new kernel (add a new entry, keep your old so you're not left with a system that can't boot).
Enter as root when your system is up and type: modprobe realtime any=1
Then exit root, run as normal user and fire up Jack.
Hopefully it works.
-Tony