Upload & Sell: Off
This is now my old rig since my MT-24EX died (I haven't decided if I'm going to replace it):
(EDIT: Eek! I didn't realize how old this thread was. This is probably way too late.)
I know it's a stretch that this might be your problem, but my MT-24EX "died" tonight. I turned it on and nothing. I thought I had removed the batteries for charging, but no.
It turns out that one of the battery contacts inside the speedlite (not on the battery cover) had gotten flattened out too much for the battery to make proper contact, even though they looked fine. I reached in there with a wooden chopstick and gently pulled each one upward a bit from the side to give them a more upward bend. Then the unit started right up.
I didn't know that this was the problem, but I did notice that when opening and closing the battery cover it would momentarily turn it on, so I had a hunch. It turned out I was right.
You didn't explain exactly in what way yours was "dead", so I thought I'd share my story.