98 jetta no rain start

i have a 98 vw jetta with about 9o,ooo miles on it. i have been having problums with my car not starting if it had rained the night befor. this has happened three times. the most recent time i am still unable to start my car. it cranks, the battery has a good charge, the starter has been replaced recently, and i have just replaced the distributer cap and rotot. nothing happened. please help!

Coil is a good bet. Do a search on this forum for coil and you will get a lot of info.