Overheating hotend

Hello all,

The hot end on my fairly new rewrap has always misbehaved. If I set the temperature to, say 250 in pronterface it will overshoot to 280+ and the firmware will then shut it off.
Relevant details of my setup:
-jhead mkII w/ 6.8 ohm resistor
-gen 6 electronics
-sprinter firmware (April 19th, 2011)

Any suggestions for how I can fix this?

Thanks!

Gen6 electronics has a bit noisy temperature measurement. I had the same problem and had to do two things: to make sure that the extruder thermistor wires are not running too close to any motor cables (I had the extruder cabling ziptied to the extruder motor cabling, this appeared to cause interference) and to raise the emergency cutoff temperature in the firmware so that it won't do a shutoff even if the temperature jumps higher for a measurement or two.