Ah, the more things change, the more they stay the same.
For the year I had AIS, (expired in March, I think) the sandbox always caused this mine and others 64 bit systems. Assorted Fx plugins would just fail to load sometimes when running the browser virtualized. It was a real touch-and-go problem. When it was working well, everything would go without a hitch. But sometimes I would have to re-launch the browser 8-10 times to get the Flash and others running, sometimes re-launching it only once would do the trick. It was extremely intermittent. But if I remember right, excluding the plugins from being sandboxed in the sandbox settings was the work around then, might still work.