Oct. 18 (Bloomberg) -- A software update at NYSE Euronextâs Arca platform triggered what appeared to be a 9.6 percent plunge in an exchange-traded fund that tracks the Standard & Poorâs 500 Index, a drop that would have erased $7.9 billion from one of the most popular securities in the U.S. Data published by the electronic venue at 4:15 p.m. New York time showed the SPDR S&P 500 ETF Trust at $106.46 compared with its opening price of $117.74. The apparent plunge in price involved 7.2 million shares in the closing auction on NYSE Arca, according to data compiled by Bloomberg at 4:30 p.m. The S&P 500 rose 0.7 percent to close at 1,184.71 today. The glitch in the exchange-traded fund, which has a market value of $83.3 billion, comes as federal regulators are trying to restore confidence to equity markets following the May 6 crash that erased $862 billion of share value in 20 minutes. Data showing the decline appeared just as Apple Inc. and International Business Machines Corp. were releasing quarterly profit statements. âIt was a mess and it was alarming that it could happen,â said Andrew Ross, a partner and global equity trader for First New York Securities LLC, who trades ETFs. âPeople were very focused on after-market trading because of IBM and Apple earnings so it was very confusing when the price discrepancy happened. But people quickly recognized it was a bad print.â Auction Glitch NYSE Arca said the ETFâs official closing price will be recorded as $118.28, a 0.5 percent gain from its Oct. 15 close. The exchange operator said its 4 p.m. closing auction in securities listed on NYSE Arca was delayed for 15 minutes because of an issue with a software release. Auction prices occurring at 4:15 p.m. will be the official closing price for all other securities except for the SPDR S&P 500 ETF. NYSE Arca will âbustâ all the $106.46 trades, according to an e-mail from exchange spokesman Raymond Pellecchia. The fund managed by State Street Global Advisors is one of the most heavily traded securities in the U.S., averaging 223 million shares a day this year, data compiled by Bloomberg show. âThe issue has been resolved,â Pellecchia said in an interview. âOperations will be normal tomorrow.â Marie McGehee, a spokeswoman for State Street Corp., declined to comment. Trading in another security linked to the S&P 500, the E- Mini futures contract traded on the Chicago Mercantile Exchange, helped start the May 6 crash that briefly sent the Dow Jones Industrial Average down 998.5 points, according to regulators. A mutual fund companyâs automated sale of the contract without regard to price and âhot potatoâ trading by computer-driven firms set off the rout, according to the Securities and Exchange Commission and Commodity Future Trading Commission report. http://noir.bloomberg.com/apps/news?pid=newsarchive&sid=aLHtrwe_p2J0 The US markets are a farce, a complete joke. And funny enough nobody on ET complaining about canceled trades ?