Problem drytek2: power

[mcp at snf.stanford.edu]

Hi!
  I was doing at 11 minute nitride etch, and about 8 minutes 
in I noticed the power had dropped to 0 and reverse power
was at 80.  I has just finished 5 and 6 minute runs with
no problem at 500 W, 0-20 reverse.  I stopped the run and
tried to retune, but couldn't get the power over 350 W.  
Everything was fine for the previous two users, and for my
first two runs...it just quit in the middle of the third run.
Thanks!
Mark Peterman