Symantec has denied that its consumer security software, including Norton Internet Security and Norton 360, is to blame for wreaking havoc on some users' PCs after they upgraded to Windows XP Service Pack 3 (SP3).

Microsoft declined to answer questions about the problem, which has emptied Windows' Device Manager and deleted network connections, preventing some users from connecting to the Internet or to wireless networks.

According to reports posted the day after Microsoft launched Windows XP SP3 on Windows Update, some users found that their network cards and previously-crafted connections had mysteriously vanished from Windows after updating to the service pack.

"The Network Connections screen now does not show any of the NIC cards. I have three adapters that used to show up," said someone using "MRFREEZE61" as an alias on Microsoft's XP SP3 support forum on 7 May. "In an attempt to troubleshoot, I tried to bring up the Device Manager, and to my surprise it is now empty."

Numerous other users corroborated MRFREEZE61's account on the same support thread.

MRFREEZE61 reported that he'd found large numbers of corrupted entries in Windows' registry, a directory that stores settings and other critical information for Microsoft's operating system. Those entries, said MRFREEEZE61, began with the characters "$%&"; once they were removed, the PC returned to normal.

Today, Symantec said its initial investigation had uncovered no cause-and-effect between its software and the corrupted registry keys, which in some cases numbered in the thousands.

"While we're seeing that this issue can affect Norton users, we don't believe we're the root cause," said Sondra Magness, a Symantec spokeswoman, in an email. "In further searches on this issue, we found a number of users experiencing the problem but who do not have Norton software and/or are experiencing the issue on XP SP2."

In a follow-up telephone conversation, Dave Cole, Symantec's senior director product management of its consumer lineup, acknowledged that users running Norton titles were experiencing problems, but said the numbers are small. "The support lines are not ringing off the hook," he said. Cole also said that Symantec had done "extensive testing" of its products with Windows XP SP3, but this issue hadn't surfaced.

And he essentially blamed Microsoft for causing the problem. "This is related to XP SP3," he said, "and XP SP3 has already had other issues specific to some OEMs and some processors."

Cole was referring to the "endless reboot" snafu that users began reporting after applying the service pack upgrade; last week Hewlett-Packard, whose AMD-powered machines were cited by most users as the only ones affected, confirmed the rebooting glitch, and Microsoft announced it would add a filter to Windows Update to prevent AMD-based PCs from obtaining XP SP3 via the update service's listings.

"People need to exercise caution before [updating to] XP SP3," said Cole. "This may well go beyond Symantec."