Bump, hopefully someone can give some advice on this one....?
Just thinking outside the box, make sure there isn't water in the keyfob itself.....
you never know though.
I suppose a good look at all the electrical places water could hide would be a good idea, also check the sunroof (if you have one) and door/boot/window seals for dirt, damage or poor fitment.
My first suggestion is always get the tools out and have a look about. I figure in this case you'll be looking for water, someplace electrical. Says either engine or passenger compartment fusebox/related wiring to me.
I suppose a dodgy immobiliser antenna (or it's connection) could cause these kinds of faults.
(banged the steering column shrouds recently?) ie; with a knee or something?, sure I've read about this happening before....hmmm
anyway, hope someone who knows your car will give some specific stuff to look at