It stopped working for me this morning as well, but I did a quick edit and now it works. I've tested it only on my config (FF 2.0.0.13). Here's what I did:

Go to Mozilla profile directory. On Windows this is C:\Documents and Settings\<username>\Application Data\Mozilla\Firefox\Profiles\xxxxxxxx.default (where xxx is some garbled mess)

In there, I found the script gpe.user.js in gm_scripts. If you use Better GReader or other extension, it'll be somewhere else (e.g. in a .jar, where it'll probably be harder to edit - so probably using the standalone script is best).

In that script, on line 182 (version 1.07d), change

var ins = body.getElementsByTagName('ins')[0];

var ins = body.getElementsByTagName('div')[0];

That's it! There may be a more elegant fix, but since it works, I'm not touching it :-)

btw, Julien, thanks for a great script! I use it all the time, very very useful.

John</username>