I was going to mention clearing the flash cache, but I checked your start date, and found you've been around here a long time, so you'd already know to try that...
I saw this mentioned under "optimizing"... think you have to turn something off in your "options" to stop/start the loading later/sooner?
But it says here, that unless you get errors, don't clear your cache...
If you experience an error message when loading the game:
Clear your browser and Adobe Flash cache.
Please do not do this if the loading takes a long time. Clearing your cache will increase load times.
As we make updates and improvements to the site, there is the possibility that an updated file will become incompatible with a file that was cached in your browser from a previous session. The symptoms you would see are if you see an error message while loading the game or if one of the two flash widgets on the top left of the screen with your friends list does not show properly. In these cases, it is necessary to clear your cache in order to get the game working properly again. Please note that your cache should not be cleared too often, as the game depends on large files cached to your browser, and having to download them frequently will slow down performance.
Found it. :^)
In the game, MAIN MENU>OPTIONS
On the Advanced tab, disable avatar rotations, and enable background loading.
Rollover (mouse) the setting buttons to see a full description of each option below them.
Hope this helps. Maybe the settings got changed somehow w/o you knowing... it happened to me once. Think it happened in practice.