You're being paranoid. Clinton knows she has no move. She will campaign half-heartedly for Obama, pay her dues, and just hope he loses on the grounds that she can run in 2012. She may pull a Lieberman (say something damaging to his campaign at a very crucial moment, that ultimately cannot be held against her as Lieberman did to Gore during the whole Florida recount fiasco) but she won't try to make a move at the convention as she does not have one.
As for an assassination, I simply don't think its possible. The secret service is going to have a small army at that Convention. Though I do think it is dumb to have the acceptance speech at Mile High Stadium with 75,000 people from a security stand point and am honestly suprised Secret Service did not shoot that down (no pun intended). A stadium is designed to give every seat an optimal vantage point. A fairly accurate pistol could make the kill shot from a decent distance in a football stadium and with 75,000 people it would be fairly easy to smuggle in. Still, I don't see it happening. I doubt tickets were sold to just anyone and if I can figure this stuff out, I'm pretty sure Secret Service can and will be going over every visitor with a fine tooth comb.