Cruise Control not in control.......

My cruise control has gone capput. When I get to cruising speed, I turn it on (and yes, the swith on the fob is set to the ON position). But as soon as I let off the gas, it acts like it is not even engaged. What could be the problem? Should I change out the entire Cruise control Knob, or is there some other item I can tinker with or replace? As always any and all help is greatly appreciated. And furthermore, thanks to all of you for your help with my problems in the past. Ya'll have saved me a good deal of cash.

check your brake light switch. on the 94 model the brake light switck is held on by a metal clip. their is a revised clip that holds the switch a lot better.