I think you may have some frozen water in your fuel system somewhere. All it takes is one drop of water to freeze in the wrong place, and you're not going anywhere. Start using dry gas on a regular basis, and keep your tank full. Don't be one of those folks who just adds 5 bucks worth of gas and never fills the tank... all that air space in the tank over the fuel is filled with air as humid as the outside air. When the temps drop, water vapor condenses and invariably finds it way to the bottom of the tank.

For now, the best thing to do might be to find a warm (40F or warmer) garage for you car and let it soak there for 12 hours or more to let any ice thaw. Meanwhile, make sure that you don't have a leaky windshield which is dripping water onto the fuel pump relay!

Check the 25 amp F.I. blade fuse that's mounted on the left side behind the battery. When it rains, it gets soaked. Remove the fuse, dry the contacts, clean up any corrosion and reinsert. If this works, then when you have time replace the fuse with a water-proof one. (http://mastercatalog04.westmarine.com/0644.asp) The H listed one for $7.99

Anthony

Try the midnight test when it's exhibiting the symptom - dark as possible; look under the hood for sparks/flashes while cranking and/or running.

Does it clear up completely when it's dry? If it's still showing symptoms, try heat and/or fans under the hood for a few hours. If this cures it, it has to be electrical. Then you could try misting water in areas under the hood while running (be careful), to see if you can provoke the problem and isolate it to an area. You could do this in the dark with a flashlight, so you can spray with the light, then test again in the dark.