I love scribefire - it is a firefox plugin that gives you almost complete control over your blog. In fact, I have grown addicted to it and won't even consider a content management system that it doesn't work with for personal sites.
But it stopped working for me the other day... and I just figured out why. My theme was causing it.
This was the error I was getting from Scribefire when I clicked on my blog. 
The issue is malformed XML - so to look at the XML I logged into wordpress admin (this should work with any software that works with scribefire like Drupal for example) and exported the site as xml - 
Once you have it downloaded - open the xml in IE or Firefox - it will tell you where the error is in my case, firefox said the error was on line 1 and showed the bad code which I recognized because I remember seeing it in the theme. I then opened the xml in notepad to make sure: 
That fist line is a line of code I commented out in the theme. Somehow, wordpress was putting that commented line into the xml feed. So - I went to the theme editor, found the comment, and deleted it - problem solved.
You may need to look through all the files in your theme for the bad code, or it could be that you have bad code or charicters in a post. In any case, opening the xml and looking for the error will give you a clue.
Good luck.