CS3: "licensing subsystem has failed"

I have a legitimate copy of PS CS3 I purchased last year..

my Photoshop wont open now, it says

   "the licensing subsystem has failed catastrophically.  You must 
reinstall or call customer sup****t."

it would be nice if the customer sup****t phone no. were in this alert, 
or were included in the box.. one would think for $650.00 this is the 
least you could expect..

why is this happening??   it has never happened before..  (CS3, Vista 
Ultimate....)

thank you...