I sometimes have problems loading java script and CSS, and i think that Url.ThemedContent is the culprit.
Everything will work perfect, but if I refresh my page multiple times fast (CTRL + R in chrome) to clear my js-cache, for some reason it just crashes my file loading.
It says that /N2/Resources/..... cant be found, and it messes the page up completely, only way to fix it is to change the web.config so that the page recycles.
Try using the N2.Management.NoZip package. If that doesn't work, it sounds like a bug, so file an issue at http://github.com/n2cms/n2cms so that the developers will fix it.