Miata is right!

And above all, DO NOT take it to a Chrysler dealer, that is NO WAY to get one of these cars running. You either have:
1) a bad battery
2) broken solder on the RCM
3) bad battery cables connections
4) mice have chewed the wiring
5) some rare issue we've never heard of

Fixes are:

1) Change the battery. (Since a jump didn't do it, I'd say this aint it.
2) Resolder the broken joint(s) on the RCM.
3) Clean up the battery cable connections, paying attention to the chassis end of the ground cable as well.
4) Buy a new car.
5) Hang out here, we will work with you and get it going.

Non-Fix:
Taking it to a Chrysler dealer.

Other Options:
Find a local shop known for expertise with Mercedes, especially the SLK320/SLK32AMG - which is what your car is, other than the Eric-Stoddard-Designed body.