Okay, the good news is, your wheel is spinning when you hit a menu item. The bad news is it is indeed the weather lookup locking up the application.
Here is what is going on: the PHP script is fetching the Yahoo weather but it is being delayed for whatever reason. That AJAX call being run prevents other AJAX calls to the same site, from the same browser and as a result you sit there waiting. I will add a timeout to the script now to prevent these lockouts, which might not fix the weather but at least will let the rest of the app function.
My guess: Your connection is being flaky or Yahoo is throttling you (I doubt it but an idea). Try going to Yahoo directly and see if it takes a bit to open or not (refresh it a few times):
Update: Time out has been added (5 seconds). Let me know if this helps. Again, if the weather times out, it won’t show the weather but the rest of the application will function.