The swoon in shares of the Chicago Mercantile Exchange ( CME) this week strikes some market participants as a harbinger of bad times for commodities trading. Whether a rough patch could be blamed on Refco ( RFX), however, is a matter of some debate. After touching a 52-week high of $346.50 on Oct. 4, the CME's stock has been steadily falling to a recent quote of about $311. Part of the decline is clearly attributable to perceptions about Refco, the big New York derivatives trader that is battling for survival amid a $400 million accounting scandal. The stock has lost more than 7% since word of Refco's travails broke on Monday. The Chicago Mercantile Exchange and the Chicago Board of Trade clear about 60% of all Refco trades. The CME says the figure for annual revenue received from Refco's business isn't available because the firm doesn't break out each clearing member's results individually. Yesterday, Refco imposed a 15-day moratorium on all activities of its offshore securities and foreign-exchange subsidiary, Refco Capital Markets Ltd. While the company said Thursday that capital accounts at its two regulated U.S. operations, Refco LLC and Refco Securities LLC, were unaffected by the scandal, on Friday it began to unwind customer and client positions at the latter. Traders said Refco Securities is the smaller of the two U.S. divisions, but Friday's move sowed more doubts about the parent's continued solvency. In a statement Thursday, the CME said Refco LLC has met all of its obligations and remains in good standing, but said it was restricting the company from withdrawing capital without the exchange's permission. Judging by the action in the stock, not everyone feels that it is business as usual at the Chicago Mercantile Exchange. Some traders even feel that the shuttering of Refco Capital Markets is a signal that the top is here for commodity prices.