The outage was "embarrassing" for E*Trade, said Leonard Purkis, the company's executive vice president of finance, who spoke at the NationsBanc Montgomery Securities conference in San Francisco today.
The glitch, which occurred shortly after the market opened, was caused by a software upgrade that malfunctioned.
"We've made some changes," said spokesman Russell Simon. "The problem is not fully solved."
The glitch was not related to trading volume or E*Trade's system capacity, which have caused problems in the past, the company said.
Other parts of the site, such as portfolio tracking and stock quotes, were unaffected by the trading glitch, E*Trade said, but its voice-recognition trading system was down for about 50 minutes.
But one E*Trade account holder told CNET News.com that his portfolio manager screen showed nothing where his stocks should be listed, although the account positions screen did show his actual holdings.
E*Trade users who contacted CNET News.com said they received only this message when attempting to log into their accounts: "Your request cannot be completed. Please try again or contact E*TRADE Customer Service at email@example.com. Thank You."
The brokerage has set up a special email address, firstname.lastname@example.org, to handle customer complaints, which have also been rampant on message boards throughout the Web. "We sincerely apologize to our customers for any inconvenience," the company's statement read.
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The SEC said that it expects 10 million individual investors to be buying and selling stocks online by the end of this year, but complaints to the SEC about Web brokerages are up 330 percent.
E*Trade management is scheduled to make a presentation to institutional investors at the Nationsbanc Montgomery Securities conference later today.