Ok I just tried to post the transaction manually. I first did the suggested "decode" and that seemed to work, I dont understand the details of the JSON-like out, but there weren't any errors.
After posting the transaction, the website returned:
An outpoint is already spent [(97675055, 1), (97435242, 0), (97475290, 0), (97480163, 0), (97381466, 0), (97409916, 1), (97420573, 0)]
Looks like MtGox tried to double spend ?