I recently tried this as I needed access to a Microsoft site that wouldn't allow access without Silverlight... Works perfectly with my Linux Mint 12 build using Firefox 8. 
Use the process described in the second post on this page (it includes altering the version compatibility number, just so everyone is clear): 11.10 - Moonlight extension not working with Firefox 8 - Ask Ubuntu - Stack Exchange
Hopefully this helps someone. Surprisingly, I didn't spend all morning trying to figure this out and that solution worked on the first try! Enjoy.
Use the process described in the second post on this page (it includes altering the version compatibility number, just so everyone is clear): 11.10 - Moonlight extension not working with Firefox 8 - Ask Ubuntu - Stack Exchange
Hopefully this helps someone. Surprisingly, I didn't spend all morning trying to figure this out and that solution worked on the first try! Enjoy.
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