Well, nothing is really jumping out at me as far as what might be hanging the render, but you do have some demanding elements, and some odd settings.
You have 5 cloud layers, which will definitely slow things down, but all of them are at low sample levels, which should give you decent render time, but low quality. You have most of them set to Optimal (default) acceleration cache, but one of them is set to "Aggressive", which is not advisable, and one of them is set to "none" which is usually not necessary (although in rare cases it gets rid of certain artifacts). You have also enabled Raytraced Shadows in one of your cloud layers, which is unnecessary unless you have terrain that will be casting shadows *onto* your clouds (which would require very low clouds).
Your render detail of 1 is probably also more than you need, especially with such low cloud samples. I'd recommend trying 0.7 or so.
To be honest it seems as if settings have been chosen somewhat at random, perhaps to see what they do, but you should always be careful with such experimentation, changing one setting at a time and setting it back if it doesn't do anything, or does something you don't want. You can also always ask for help on settings, of course.
I can try your render myself tomorrow with some settings adjusted as per my comments above. Let me know if you'd like me to do so. Or you can continue experimenting yourself, with the above feedback in mind.
- Oshyan