you just turn it til the tabs line up and pick it out of there with a small screwdriver

 

I've had this happen to me with OEM fluid... Flushed it multiple times and it doesn't help in the long run. It'll stay off for a couple of days and come back on. Only thing I can think of is to replace the brake reservoir for a permanent solution. I'm pretty sure this isn't fluid related.

 

could be a bad switch

 

I've had the same issue (and been running with the MPC disconnected) for years now. Finally decided to fix it and picked up a used master cylinder from a wrecked car for $50. Try the Want to Buy forum to avoid the cost of a new part.

I'm speculating here, but I did lots of brake bleeding in my day and wasn't always careful to keep the fluid above the Min line... Could the float be damaged by pumping the brakes (during bleeding) while the float is no longer immersed?