I have the exact same problem, but with an MMO game of 1.7Mb. Clients with the newest chrome/flash cant cache the game in the browser. If I configure Chrome to use the system flash player (v14), the game files are cached as always did. The problem seems to be related with the flash 15 embedded in Chrome.
The strangest thing is that if I create a separate html page and embed the SWF there, it seems to be cached fine. But in the original dynamic page where the game needs to be embedded it doesn't get cached.
rzuffi, did you try embedding your flash in an static html file?
Regards