That sounds like a problem that I tried for years to fix. Eventually, I got myself on a ladder on the outside and a helper on a ladder inside and sprayed the heck out of the area with a water hose.
The problem turned out to be a window. The glass was not sealed to the wood frame, and when the wind drove the rain, it came in and ran down inside the wall to the first floor in surprisingly large volumes. It usually came out around an electrical outlet.
My advice is: go over the area, especially the windows, with a strong water hose.
I had spent lots of time on the roof, in the attic, and caulking around the OUTSIDE of the window frames, but never thought of the glass-to-frame seal.
[This message has been edited by rpxlpx (edited February 26, 2003).]