Sounds like the same problem my buddy is having with his brand new SAE-300.... his does the same thing, but only jumps to low idle for a split second than right back to high idle and stays there....  i called the local Lincoln guru and he seem to think that the idle solenoid is out of adjustment or else there is something wrong with the board.  My buddy is going to take it in for him to look at asap.
Ill let you know what he finds out.
Later,