Yep, when it first happened in February, I bled it and it was good for about 3 weeks and the problem returned again. Since I can't find any leak and the reservoir isn't going down I'm suspecting that it's the master cylinder. I actually tried taking it out over the weekend but OMG, that thing is as tight as a virgin (

). Seriously, no room to work down there. It got so bad I ended up having to put everything back together and will be taking it to a shop to do it cause I could not get it out from the little space that it has.
BTW, I still use the gravity bleeding technique you taught me back in 2006 as it's still the best method I found for bleeding clutch systems. Thanks bro!!