| I had a similar thing on a (well) used ST2. Rear brake seized on and I was forced to a stop. Couldn't even get out of the trafiic until it cooled down and released enough to roll it. Who say those rear brakes don't work!!!!
I never could get it sorted, until I got hold of a spare caliper-master cylinder off another bike and put that on complete. Not a very technical way of problem solving, but I was getting desperate at that point.
Problem is - once it has seized on it will ahve generated so much heat that it'll boil the fluid. You're fighting a losing battle then because it'll not work properly anyway.
Good Luck | 
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