[Plugin: W3 Total Cache] Preloading don't work [extremely important please help]

Hello,

first gz with the plugin, its just great.
We are an internation new company that want to switch from our old website to a new one created on wp, also we want to use this cache plugin to speed up the website. The problem is that in our tests the cache preload was working just fine, it started to cache all our categories, posts etc and serving to our vistors the cached files.
Now we are trying it at our live website, but it dont work, files are not beeing uploaded, (there are about 150.000 – 200.000 posts).
Please can some one help us with this issue ? its extremely important for us.

Thank you.