Dynamic loading of JavaScript libraries is sometimes broken in IE (in rare cases)

Problem is in this code:

addScripts : function(scripts, callback) {

var _ = T5._;

var loaded = _(document.scripts).chain().pluck("src").without("").map(this.rebuildURLIfIE).value();

var topCallback = _(scripts).chain().map(Tapestry.rebuildURL).difference(loaded).reverse().reduce(
function (nextCallback, scriptURL) {
return function()

{ this.loadScript(scriptURL, nextCallback); }

}, callback).value();

// Kick if off with the callback that loads the first script:

topCallback.call(this);
},

In the nested callback, the "this" variable is not set to the right value, at least not inside ie. Need to fully qualify (Tapestry.ScriptLoader.loadScript()) or other bind this.