I seem to be having the same problem as Sledge with my Mac Pro running 10.7.4. That is, "Mount It" is not working. I just so happened to have a backup startup volume running 10.7.3 and there was no problem there, Funny thing is, I have a MacBook Pro running 10.7.4 and "Mount It" works fine there. On MacBook Pro I'm running Toast 11.0.4 only, but on Mac Pro I'm running both 11.0.4, plus 11.1 beta, so I'm wondering if beta install has something to do with.
If anyone figures out a fix, please post here.