I have a model with 19396 frames of animation
That is insane... Why? 19396 keyframes?
You can increase the nexus. Your model is highly detail with so many faces. Um I would say reduce the keyframes.
55 bones is high too right ?
info from manual...
Without a bones shader, bones animation needs more memory space and more rendering time than vertex animation. When you need huge armies of animated models on the screen, but have only the Free or Extra Edition, you might prefer vertex animation. Using a bones animation shader (Commercial Edition C or above), bones animation renders remarkably faster than vertex animation.
Bones and vertex animation both use linear interpolation between key frames. This can lead to deformations when the movement is nonlinear (as in a rotation) and the 'gaps' between the key frames are too large; for example, limbs can then get thinner and thicker during the interpolation. This can be solved by using more key frames and taking care that rotations don't exceed 15 to 20 degrees between them.
EDIT* By the way both error refer to pre-allocated memory not available system memory. With the engine you can increase this, but from what you say it looks like MED can't load files large then 2 GB's at once.
"Your computer is low on memory"
12 GB just not free. The engine 'grabs' memory so it will have enough for the level through the nexus setting.
Ok I know little so hope I don't misinform.
