Internet explorer 7, jquery 1.4.2

Internet explorer 7, jquery 1.4.2

I am using Rails 3, jquery 1.4.2

All my javascripts files (jquery.js, main.js and myutils.js)
are loaded. Everything works just fine in firefox 3.6.4

However not in Internet explorer
The problem is the following,

In file myutils.js I have a simple function defined like
function dosomethingusefull(){
      alert('hello world');
}

in file main.js I do the following
$(document).ready(function(){
      dosomethingusefull();
      alert('function dosomethingusefull called');
});

In firefox the function dosomethingusefull() is called, in Internet explorer 7 it is not??
Can't believe I am doing something wrong, however this must be the case.

*) I am not a Jquery beginner, used to work with version 1.3 and never had this problem.
**) Javascript enabled in both browser, obviously :)
***) Firefox and Internet explorer don't report any javascript errors.