That happens to me quite a bit.
1) Stop slouching in your chair. No, you do too. ;-)
2) The chiropractor helped alot. Fortunately, my insurance covered it. The drugs and other crap just exacerbates the condition.
3) Start doing back exercises and stretches.
4) Get up and walk around every 30 minutes at work. Set a timer if you need to.
Interesting explanation as to the cause of the collapse: according to my doctor, there are organelles in the muscles of the back that act as strain gauges. If a muscle detects too much strain, it sends a signal to the brain that causes all of your muscles to go limp immediately. Hence, the collapse.
Also, there are nerves in the joints that turn off every time the joint flexes. If you try to move a joint and it doesn't move, the nerves don't turn off, and you feel pain. Most back problems of that nature can be attributed to insufficient flexibility. I have a series of vertebrae in my lower back with decreased range of motion due to an old injury.
