The NYSE Summation Index has rolled over. Look at the higher low that $NYSI made in early July 2010 versus June 2010 in contrast to $SPX with a lower low. Notice how the current top in $NYSI indicates weakness with a lower high from the previous peak in October (and lower high from all major peaks over the last year). Again, this contrasts with $SPX.
It has even formed a bearish Head and Shoulders pattern since July 2010.
The signal performed very well over the last year: