Sarah reports:

This weekend there was a problem (http://googleblog.blogspot.com/2009/01/this-site-may-harm-your-computer-on.html ) with the implementation of Google's malware filters. Gmail's spam engine uses those filters (among hundreds of other signals) to help protect our users from malware, and so between 6:00 a.m. PST and 8:00 a.m. PST, we mistakenly sent some legitimate mail to people's spam folders.We've rolled out a fix that has restored these messages to most people's inboxes, though to be on the safe side we'd still recommend that you check your spam folder if there was a critical message you
expected to receive between 6am and 8am PST on Saturday.