The Securities and Exchange Commission (SEC) said it is investigating the past accounting practices of Network Associates.
The news follows similar probes involving Computer Associates, Global Crossing, Qwest and Worldcom.
Network Associates said because of the investigation, it would postpone its bid to acquire the shares of McAfee.com that it does not already own.
The company had made a $211m bid for the antivirus site earlier this month, but McAfee rejected the bid this week, saying the offer was "financially inadequate".
The SEC said it has launched a formal inquiry into the computer security software maker's fiscal 2000 accounting practices.
During a conference call, Network Associates chief executive George Samenuk said the SEC contacted the company informally after it announced on 26 December 2000 a revenue shortfall. He said Network Associates would change the way it booked revenue from its distributors.
In that statement, the company warned that it would post a net loss of between $120m and $140m for the fourth quarter of 2000 and that its top three executives, including former chief executive William Larson, would resign.
Samenuk emphasised the company had reviewed its 2000 accounting with its outside auditors, PricewaterhouseCoopers, and that it believes it is sound.
"We are going to resolve these issues," he said. "We intend to fully cooperate with the SEC."
"We do not expect this [the ongoing SEC investigation] to have any effect on our current business," he added.
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