Most of the time, the loading process stop for network connecting reason, and that depends on your server, your browser and the network state. And yes, sometimes the page stop from downloading the ressources, and cocos2d-html5 will wait.
That’s a common issue for web applications which need a ressources preload, especially on mobile version.
I believe there is no better solution than cutting your ressources files size. But if your page doesn’t load a great amount of ressources, keep me in touch, maybe there is some other reasons.