Take a look at your rear brake bulbs. Sometimes, there's a short in the tail lights socket, causing the bulb socket to melt. Maybe there's a short circuit somewhere. To do a test, try removing both rear brake bulbs and both rear flasher bulbs, on both sides, to see if that's the problem. If your cruise control disengages, it's probably because the cruise control module receives voltage through the brake circuit (the brake bulb), causing it to disengage, just like it would if you were applying the brakes.
Yves.