For those of you who were suffering similar problems:

Using Google Reader in Firefox 2.0.0.4, and not being able to load Feedburner feeds from other blogs.

The solution was simple: Disable the Adblockplus extension. Apparently Adblock was updated at the same time as FireFox, and something they did caused Google Reader to act funny. Simply disable Adblock on the Google Reader URL and all should be back to normal.

The simplest answers are usually the correct ones…..