I would just like to chime in and say I have the EXACT same problem. With my car, somewhere between the initial test drive and the pre-purchase inspection, the trip odometer stopped working. I would guess somebody tried to reset it while it was in motion.
Every tenth of a mile, it clicks, and the speedo jumps at that exact time (~1-2 mph). The path I'll probably take is to have the odometer repaired at a VDO shop. That clicking can't be good for the rest of the internals. I've often read that the odometer may follow a broken trip odometer. My cruise control is inoperable, so, I can't relate to you there. But, if the cruise control jerks at that same moment as the speedo, I would think it might be related. Having the odometer repaired would be my first step.
Good luck, and I'll be watching this thread
