Probably you're familiar with the sharing button (at least on Firefox and Chrome) offered by Google reader to help you share stuff that don't have feeds. Today, for some reason I realized that mine wasn't working!
To solve this, all you have to do is set _IS_MULTILOGIN_ENABLED a variable that's not defined (but used) in the script file in the button script. So add something like:
// or better
at the beginning of the button script, just to set _IS_MULTILOGIN_ENABLED before it's accessed as "undefined" in the script.