Hi bruno,
I see that you mentioned caches, but I'd just like to confirm that you did clear them both (the browser cache and the flash cache). Failures to load in single player are usually always cache related. After you clear out be sure to re-start your browser too.
If you run into this situation again, try resuming the game in a different browser just to see if the browser itself has anything to do with it. If you have problems with FireFox, but it runs normally in IE or Chrome then that would point to a browser setting. Switching browsers for a round or two is usually a good first effort to try and localize the problem.
Let us know if you're still experiencing issues.