Are you sure you have 1.3.1.0 and not 1.3.0.1? It's easy to get the numbers switched when reading them (I really wish they'd done an extra build or something just to avoid the risk of confusion). If you are using 1.3.1.0, try redownloading the FBX plugin - 1.3.0.6 may be a point too old for the current version of D|S, but I'm not certain (and I can't think why they'd have relaesed it for 1.3.0.1, since I'd have expected that to fail as too new).