Problem after adding UI1.9

Problem after adding UI1.9

After adding jquery ui 1.9 to my jquery mobile web app I am getting the following error in firebug

string is undefined.

This error occurs in jquery-1.6.4.js at line 622 this is the code
  1. camelCase: function( string ) {
    return string.replace( rmsPrefix, "ms-" ).replace( rdashAlpha, fcamelCase );
    },
I did a serch through all the js in my project and the only place I can find any reference to camelCase is in jquery.mobile-1.1.0.js line 1384

This is the line of code


  1. return nsNormalizeDict[ prop ] || ( nsNormalizeDict[ prop ] = $.camelCase( $.mobile.ns + prop ) );

Not sure where the issue lies, and which forum I should be posting on to find a solution, but any help would be appreciated.