It seems that a large number of Symantec PF users have been suffering a bit online lately, at least the ones that use IRC. According to varied reports, due to a particular flaw in a method Norton uses to protect a PC from anti-spyware can cause them to be kicked offline if another user so much as says a particular phrase.

A Symantec spokesperson said the "startkeylogger" trick affects only a small number of its customers (read: those geeky enough to frequent IRC) and works because its Norton products "inspect the user's Internet traffic and block the secret commands that malware writers send to their malicious software that they deploy in the field.
Symantec is workiing on a fix, which will be able to applied via the standard automatic updating their products do with LiveUpdate.