Back light failing- HW vs. SW

I have been having intermittent back light failure.
Screen display and data input are OK
inconsistent action
Sometimes works fine
sometimes intermitent
sometimes fairly long lasting
(I guess it ain't constant if it comes back, eventually)
Torque on case sometimes brings it back in one of the above patterns

Any sugestions as to what level this may be happening ?
I was intriguesd about it posibly being software
when I saw the program for further dimming on the digitizer calibration
folks site, but this is acting more like hardware.
I am just trying to get a bead on what level before I tear into it

Sadly parts prices have eclipsed used models
but I need to get two more years out of this puppy, 
hoping against hope for the TX phone equivalent


Richard