Jeep Cruise Control Problem

I have a 1999 Jeep Cherokee Sport that has developed a cruise control problem. The car has 73,000+ miles on it. The cruise control is very lethargic in responding to acceleration commands.
This occurs when I'm returning to a set speed after disengaging and when pressing the Resume Speed control for accelerating to a higher speed setting. Also, the car loses speed on even relatively minor inclines and is slow to accelerate back to the set speed.
The cruise control worked fine until now. It feels like something is out-of -adjustment. Maybe there's a part that just suddenly wore-out.
Any suggestions?

I don't have any real experience with them, but my understanding is that there is a vacuum diaphragm that controls a cable to the throttle. My guess is that the diaphragm is going bad. I don't know how to check this, but someone lurking on the forum should or you might ask someone at the parts store.