Would love to see an answer to this -- my '97 w/1.6L developed the same issue after moving to FL, ~75,000 ago. Of course, she has 576K on her now, so I suppose that it's to be expected, but suspect (after replacing fuses and checking connectors) that it's humidity-related. I've found that when our weather finally gets dry, the cruise will kick back in, but with the littlest bit of moisture, back out it goes.
She's also suffered issues with her horn spontaneously going off randomly and not stopping unless disconnected - again, always happened during heavy rain periods (even when living in VA). Solution - just leave it disconnected - not being a "honk person" hasn't really posed me any problems and been that way for 4 years. Reason I bring this up is I wonder if the two aren't connected somehow as they are both initiated off the steering wheel in this car. Is there an underside connector that fails that feeds both electrical functions?
Your cruise control cable is adjacent to the accelerator cable, in an open box under the hood, right about in the middle of everything. When I bought it, a few months back, my '98 200sx had a habit of revving up to 4000rpms when I put it in park. I was already poking around under there to determine what to do about my timing chain issue, which issue orientation will really help you think about all the related mechanical issues you might run into. In my case, the cruise control cable had a loop at the end of it, which loop got caught under the accelerator cable, which was loose on its guide - just enough give to overlap the adjacent spool, catch that loop, and get pulled taut, so rev up. When in park. The solution was to adjust the tension on that accelerator cable. Simple 20second fix. Your solution may well be to check that the cruise control cable is nicely wrapped around its guide/spool, without too much slack, and engages when you hit the switch. It may be slipping off some guide, with moisture. Maybe the guide needs replacing, or a talking to with an emery board so it catches even when moist, or something.
