I too have suffered from debilitating low back pain for years (two disc herniations). It took me a couple of years but after learning Pavel's and Stuart McGills Abdominal Bracing technique (which is taught at the RKC certificaiton) cured my problems. I think most lumbar spine issues (including a spondilo) will respond very well to static and dynamic stabilization exercises. You must find what your NEUTRAL spine position is and teach your nervous system how to maintain that lumbar/pelvic position while you train. It takes time, but rest assured you can get better relatively quickly.
I agree with Cecilia, you probaly need to back off on the weight and the total volume (reps and sets) until your pain is diminished. Your body is obviously not responding well to the 24kg.
The exercise that really helped me was the Kettlebell Renegade Row and an exercise that I invented call the Kettlebell Prone Bridge. The objective is to keep the pelvis and lumbar spine motionless. It is very tough to master but is absolutely ESSENTIAL to lumbar spine function.
Check out the link of the video for the KB Prone Bridge that I posted on my blog some time back:
Lift Kettlebells: Video Player > Kettlebell prone bridge
Hope that helps!
E-mail me with any questions. I am rehab a lot of people with low back pain:
franzsnideman@earthlink.net
Best,
Franz Snideman RKC TL
Franz Snideman RKC Team Leader