Blog sometimes loads as XML

A site link may help, otherwise, I have never heard of this unless you are clicking a link or navigating otherwise to the wrong link.

I suspect a plugin or your custom theme – switch to default unedited theme, deactivate all plugins and run site (clear local browser cache after site changes and prior to running as site visitor).

You’ve got something wacky with feedburner. I see a feedburner feed URL and also a WP feed in page source. And a different WP default feed for the home page. Get that sorted.