I think there are several reasons the stocks underperformed today.

1/. There is a new article going around about resource nationalization that seems to be spooking some investors.
http://www.silverstrategies.com/story.aspx?local=1&id=17168

2/. The latest consumer credit report released yesterday was frightening.
http://market-ticker.denninger.net/archives/1418-The-Governments-Effort-Has-Failed.html For those who are paying attention this adds risk to some of the under capitalized juniors.

3/. The stocks have performed very well lately and with the 1000.00 mark being tested for a third time some have decided to take profits.

4/. The deflationists Bob Precter, Bob Hoye, etc. are calling for a reversal in gold and especially silver and the general markets. They have a large following.

I personally have reduced some of my positions in the stocks and have moved more toward physical. I am waiting patiently to see if the breakout occurs now or if we will have to wait again.
If it fails I think we will get a big fall in the PM stocks quickly as the hot money bails.
If it succeeds many of the smaller stocks could easily double in a few days.

this is a risky business good luck