This problem is very difficult to reproduce and seems to be very timing dependant.
The shortest ammount of code I can get it in, is a bit odd, to get this to crash, first click 'Crash', after the alert, once it starts animating/flashing.. click on the flash object. Either close the window or dont, you should crash shortly..
This issue happens randomly though and without such weird conditions..
In short, the issue seems to be when having a flash window inside of a div thats being animated by blockUI or by jquery.animate, i'm sure there are many other ways to get this issue to surface.
My bug report XP (FF 3.0.8) -> http://crash-stats.mozilla.com/report/index/19c59526-0db2-43f1-a89a-860b32090411
Verification (FF 3.6a1)-> http://crash-stats.mozilla.com/report/index/3f3a929d-8a58-46df-89a1-30aec2090411
Windows 7 (FF 3.0.8) -> http://crash-stats.mozilla.com/report/index/7c15af54-de5d-4f2f-9493-c14fd2090411
Seemingly related bug -> https://bugzilla.mozilla.org/show_bug.cgi?id=486809
This bug on mozilla https://bugzilla.mozilla.org/show_bug.cgi?id=487938
Complete Code In .Rar Format
NOTE: Sometimes this will crash without you ever having to click on the flash object... it seems random'ish... You must have Flash installed to see this bug... and it doesn't always happen, it appears more often on larger pages.