that you have uploaded it :) this bug was really annoying. this is how i did it before (copied from the internet&pasted&modified):

// Add jQuery
var GM_JQ = document.createElement('script');
GM_JQ.src = 'http://jquery.com/src/jquery-latest.min.js';
GM_JQ.type = 'text/javascript';
document.getElementsByTagName('head')[0].appendChild(GM_JQ);

// Wait until jQuery is loaded
GM_JQWait(onJQLoaded);

function GM_JQWait(onjqloaded)
{
  if (typeof unsafeWindow.jQuery == 'undefined')
   { 
    window.setTimeout(function() { GM_JQWait(onjqloaded); },100);
   } else
   {
    $ = unsafeWindow.jQuery;
    onjqloaded();
   }
}

function onJQLoaded()
{
  // function using jQuery
}

but i cannot use xmlhttprequest with that