Had a problem today with the feeds received from Google Reader. They all disappeared.
When this happened I was fearful that something I've been doing angered the Google gods, but apparently I wasn't alone in suffering this loss.
Fortunately, the export.opml file that I maintain on the site worked as an instant restore.
Nothing appears to have been lost in the process. (Knocking on wood repeatedly.)
Anyway, if you notice any unusual stuff when viewing the topics -- or the topic feeds you are subscribing to start acting up -- the problem is apparently widespread in Google Reader land.