do you have a sealed bearing bb or loose bearing bb? i have had similar problems in the past with both types of bb. i found that if you have a sealed more modern style of bb the clicking is usualy bearings giving way.some times you can just replace the sealed bearings. if you have an older bb then it could well be the bearings just need a sevice and tighten.
you could always try locktight thread lock. its used on cars to stop nuts and bolts undoing under vibration. around £4 from halfords. i use it on my bikes.