You can read the latest analyis I've been doing for the BBC about Flame here. It's based on information made available by Kaspersky, a summary of which you can read here. In short, it looks as if some source code wassared by the developers of Flam eand Stuxnet, from an early version of Stuxnet. However, after 2009 everytyhing suggests that the developments of the malware each went their separate ways.
There is still nothing in the code that we can see, or has been reported by others that suggests any particular group, country or government developed Stuxnet or Flame.