gene arensberg tells us why silver's latest advance was stopped:

COMEX commercial futures traders, who have added heavily to their gold net short positioning over the past three weeks, jumped all over the short side in the silver futures market this week. That follows four straight weeks of higher silver prices and a roughly $2.00 advance for the second most popular precious metal in U.S. dollar terms (measured on Fridays).

As silver added 33 cents to $17.26 (measured on COT reporting Tuesdays), Commercial traders boosted their net short silver positioning by a big 4,859 contracts (11.9%) to show 45,799 contracts net short as the open interest only increased 3,882 to 112,130 contracts open.

So, apparently the largest silver futures traders felt that silver had advanced enough to fade the rally with silver metal in the USD $17s. That increase in commercial net short positioning makes for a fairly large jump in the relative commercial net short positioning from 37.8% to 40.8%.

http://news.silverseek.com/SilverSeek/1268838249.php