NEW YORK (Bloomberg) ? XL Capital Ltd. shares plunged as much as 12 percent yesterday after the property and casualty insurer said a ruling on its purchase of Winterthur units would reduce earnings in the fourth quarter by $830 million.

XL said in a statement after the market closed on Wednesday that it may get about $575 million from Winterthur after a dispute over reserves at some insurance operations XL bought from Credit Suisse, based on a draft ruling from an independent actuary. XL was seeking about $1.45 billion.

?It?s a very disappointing decision by the arbitrator, but it?s quite likely that the management team at XL Capital will be successful in replenishing some or all of the lost capital in due course,? said David Anthony, an analyst at New York-based Argus Research Corp. who has a ?hold? rating on the stock. XL said it plans to sell new shares ?as quickly as possible?.

Shares of the company fell $5.83 to $67.91 in New York Stock Exchange composite trading as of 12.18 p.m., after touching $64.83 earlier today. The stock had fallen five percent this year before today.

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