Transmission Slipping in third 2003 5sp Auto

50 miles into a 500 mile trip this weekend the trans in my 2003 Mazda 6 3.0 with added trans cooler (147K mi ) started shifting really harsh on the highway and the "AT" dash light was on. Wife says turn around - I say lets keep going.
At the first stoplight 200 miles later it won't even move...F***. Wife is pissed "I told you to turn around". Push it off the road and call local Enterprise rental 2 min before closing time... they left early.
Just for grins I try the car and its back working - even the AT light is out but when it hits 3rd gear it revs up. That's not good. Fluid was OK but a bit burnt smelling. I made the rest of the trip by manual shifting to stay out of third gear - got home fine. I'll be calling trans shops tomorrow but any comments / tech advice appreciated.

Sounds like 3rd gear clutch bands are shot if you ask me.

Well that was an adventure and I never dreamed I would take the trans apart in the car and fix the problem which was suspected to be a cracked high clutch (3rd, 4th & 5th) piston but once inside I found the manifold seal rings that are part of the cover were worn and causing leakage feeding the high clutch. Also now I know that the CEL P0740 "Torque converter circuit malfunction" fault I have been having for the last 100,000 miles was this very problem developing as I am now driving fault free with firmer shifts than before. I wrote a big procedure of this detailed repair job with pictures in the attached PDF for this JATCO JA506E transmission.https://dl.dropbox.com/u/27419177/2003%20Mazda%206s%20%20%205%20speed%20Automatic%20High%20Clutch%20repair.pdf and the helpful manual is here: https://dl.dropbox.com/u/27419177/Trans%20Manual%201738-1E-02D.pdf

After working perfectly for 6 mos it seems that the high clutch is again loosing pressure (likely the seal rings again in the side cover manifold).
Just beginning my investigation as to what might be causing these seal rings to fail again so soon (wrote to the guys at www.atra.com.
Symptoms are a whining noise from the transmission - obviously an internal pressure leak - once the trans gets warm (about 5 mile drive) the pressure is low enough to cause slippage in all gears.

Anyone have any info that may help?