Dropouts since Saturday 1/25/03 only affecting web traffic?

According to Matrix Systems (http://average.miq.net/Weekly/markR.html) there have been two additional dropouts of global Web reachability on January 26 and January 28. These dropouts have been for few hours or so, but nearly as large as we saw from the SQL worm. However it doesn't seem to affect other network services, as measured by Matrix. Just the measured web servers. The most recent was tonight from 3-5pm and again from 5-7pm EST (http://average.miq.net/) Any ideas what is causing them? Measurement artifact? Are you seeing something strange on your networks about that time?