I've upgraded my blog to BlogEngine 1.5.0.7 and then I got a Java Error saing BlogEngine is not defined. The solution is the following.

Download the latest version from codeplex.
Extract blog.js and open it in your favorite editor and look at the code.

// global object
BlogEngine = {
    $: function(id) {
        return document.getElementById(id);
    }

The first row is to be deleted, so the start of the file will look like this.

BlogEngine = {
    $: function(id) {
        return document.getElementById(id);
    }

Upload the file and restart your .NET application. Edit your Web.Config to get the server to recompile the site.