RSS feed and index.php issues

Hi there,
I'm having two problems.
1. For some reason my RSS feed has suddenly stopped updating and now gives an error "500 - Unable to load renderer class"
http://whizzbangsblog.com/index.php/article-archive?format=feed&type=rss
I've also tried using the URL from the setup area and it also give a 500 error:
http://whizzbangsblog.com/index.php?option=com_easyblog&view=latest&format=feed&type=rss

2. You will notice that index.php is in the URL. I'm really wanting to remove that from ALL easyblog/site links and no matter what I do I end up getting an "page can't be found error". I have turned on/off URL Rewriting in Global Settings and have ensured that my version of Apache has mod-rewrite installed and functioning.

Thanks for your help.

Michael