beltfed,
It sounds scary. Does the pedal stay firm but the rig doesn't slow down, or does the pedal go spongy and 'no-slo'! I think if you have a good, firm hard pedal but 'no-slo' it's a lining issue. About the only enemy of a modern lining is heat. If the brakes were adjusted too tight and were creating heat as you drove, they soon would overheat in traffic and your stopping ability would go down the drain.
I think this could happen without the usual smell associated with cooking brakes. You mention new linings on the front...how about the rear! If only half the system is trying to do the stopping, it will fail pronto. I don't see what kind of rig we are talking about in your profile...probably a 1/2 pickup. If you have a neat IR temp gauge, shoot all the wheels next time it happens...you might find out something interesting.
Stuart
