From what I have read there should be a few TSB's around this issue. There are a couple things it might be

first two are for if you have a sunroof)
1. There is a joint in the roof that was not sealed properly, this can sometimes cause water to drain down into the panel.
2. The drain tubes get clogged with crap and water sits in the sunroof area, and due to the slope of the roof, it drains downward to he fuse panel.
3. It could be the windshield seal.
These are some of the things I have come across. My solution so far has been lots of plastic bags under the dash, above the panel. It is going to rain here today, so I just checked them.
Nate