Every so often, like right now as I post this, all pages that have AdSense on them cause my browser to hang. I'm using IE 6 on Windows 2000 Professional and it works on other PCs with the same version of IE. I contact Google but they always tell me the problem has gone away and by the time they reply it has! My concern, and it should be all of your too, is that there are a small percentage of people out there with a particular configuration who are experiencing the same thing.
I occasionally experience the problem you describe, like a few minutes ago, probably the same time as you. I also am running IE 6 on Windows 2000. The problem is gone now though. It usually only lasts a few seconds, so I haven't been complaining.