Shares of LaBranche ( LAB) were among the NYSE's losers Friday, tumbling 21% after the specialist trading firm warned of a big second-quarter loss. The company sees a loss of about $23 million, with an operating loss of about $5 million, or 8 cents a share. LaBranche also said its loss would include noncash costs of about $17 million related to a decline in the estimated fair value of the restricted shares of NYSE Group ( NYX) that it owns. The company attributed the operating loss to a decline in principal trading revenue in its specialist and market-making business. LaBranche expects to post principal trading revenue of about $20 million, down significantly from the $47 million it posted during the year-earlier quarter. "These lower principal trading results were due to adverse market conditions in May and June 2006," the company said. Shares were trading down $2.65 to $9.79. 3M ( MMM) slid 7% after the consumer and industrial conglomerate warned that second-quarter earnings would miss its previous guidance. The company continues to expect earnings of $1.14 to $1.17 a share, but that now includes one-time gains of 8 cents to 10 cents a share. Without the one-time items, earnings would be below earlier guidance. On the top line, 3M sees revenue of about $5.7 billion. Analysts polled by Thomson First Call project second-quarter earnings of $1.17, excluding the one-time items, and revenue of $5.71 billion. "This second quarter performance was impacted in large part by lower than expected sales volumes and higher than anticipated new capacity start-up costs in the optical systems division, a part of 3M's display and graphics business segment," the company said. For all of 2006, 3M anticipates earnings of $4.55 to $4.65 a share, including the one-time gains of 8 cents to 10 cents a share. Analysts project earnings of $4.66 a share. Shares were down $5.96 to $75.43.