Rss – live bookmark failed to load

Hello all,
after reviewing the post regarding this topic, and not being able to find a solution, I decided to post my question to the forum…
My feed at : http://www.miamidrums.com/feed/ works, at least I can see it, and even read it at google reader. My problem is that Firefox live bookmark gives me an error, no matter how I subscribe to it…It used to work, not long ago…I did some modifications to the blog – a notification plugin and a WPSMTP mailet – but I really doubt any of those modifications render the rss not readable by Firefox…any ideas?

Thank you all in advance!