Hi Guys -
thanks for the responses. I spend today with the hose and sprinkler and believe that I have determined the source of the leak. It appears that the water is getting behind the siding between the lower portion of the window and the j-channel (hope that is the right term). This window sits above about 10" above the deck and is directly over the patio door.
here is an image (sorry its really rough) of what I'm seeing after pulling some siding off...
The green represents the window, the red is the OSB wall and the purple is the j-channel under the window. I believe the water is getting in between the window and the channel. The siding itself obviously sits between the vertical portion of the channel and the lip of the channel. Looking at this setup, there is nothing to prevent any water that gets between the channel and the window from running down behind the channel and behind the rest of the siding.
When the house was built, they wrapped it in tyvek, so when I actually got the siding off, there was one giant tear in the tyvek which I patched. I assumed the water was getting in there, since the rest of the tyvek should be waterproof. I put everything back together and it still freaking leaks.
Can anyone comment on whether or not my little image is correct? It doens't make any sense to me (I'm an mechanical engineer by trade) to let water get between the window and channel only to let it run down behind the rest of the siding. Is there something missing? The other kicker here, is ALL of my window are exactly the same way. I could have water running in all over the place. UHG, I can feel my blood pressure going up already.
Again, any and all help is greatly appreciate. Tomorrow I'm going to take the siding off again, and the first deck board next to the house. I'll post pictures, hopefully that will give a clearer picture.