Ok, well I just downloaded LL from my own website again and tried fiddling with your model, and it seems to work fine. I'm not sure what's happening - try redownloading the exe, and see what happens.
It's unlikely, but it might be to do with the way you're rotating limbs. Try just loading the object and then set a keyframe - if it works, then we'll take it from there.
Quote: "why does the model import into LL "upside-down"? "
Ah. Your 3d model maker is exporting the .x file with mismatching axes - sometimes the z-axis is into the screen, other times it's out of the screen, sometimes X, Y and Z can be completely swapped round. This isn't a flaw, it's just that different programs define the axes differently.
There should be some settings to change this, but a quick fix in LL is to select limb one (the 'root' node) and rotate it x=270 and z=90. Never modify this again, and the object will be the right way up. (in DBC, all the limb commands reduce to the object commands when you use a value of zero, which is what LL calls "Limb One")
As to a good size for your object, it's entirely up to you but thre is no definite sizeing required. A six foot person could be drawn as 6 units high, or 12, 18, 24, 3.234567 units, whatever. As long as everything is in scale with everything else, it doesn't matter what size you use.
Just as a general rule of thumb, the distances involved (for example, when a persone walks, or you move the camera) become more manageable if the character is only 20 - 30 units tall. that way, you can move the camera say 5 units per sync, instead of 50 or 500.
Hope this helps!
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