I can only assume that it's the rewrite rule in the Rails context of the EasyRailsWithsuEXEC template. I have not added/changed anything to do with rewrites as I'm not knowledgeable about them.
RewriteRule ^$ index.html [QSA]
RewriteRule ^([^.]+)$ $1.html [QSA]
Is there some place else in the configuration that I could find a rewrite rule?