Flash .271 breaks when run sandboxed in Firefox 14.0.1. Runs fine when not sandboxed.
Found a solution here: http://forums.adobe.com/thread/1018071?
To disable Protected Mode, add the following line to your mms.cfg file located in:
Windows 32bit: C:\windows\system32\macromed\flash
Windows 64bit: C:\windows\syswow64\macromed\flash
Protected mode changes permissions for flash and since I sandbox my internet facing applications I don't require it.