Hi Matt, MoI is just plain old running out of available memory when that happens. MoI is a 32-bit program so it's only actually able to use 4GB of your memory and a 375mb file is quite large in size. You will probably need to get that exported out from whatever application is writing it into a few separate files instead of one single gigantic file.

> Does MOI have an upper limit of the file size it can import?

There is no one specific limit, since it depends on what kinds of things are in the file - for example like AW mentions above if there are a lot of block instances inside the file that will balloon into a much larger size in memory at load time as they each become an individual object at load time into MoI right now.

Also if the object has a whole lot of little tightly curved pieces in it, that will consume more memory for display mesh generation when it is loaded.

You can lighten the memory load somewhat by changing a setting to use a rougher display mesh, that's a setting under Options > View as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4643.2

Setting the "Mesh angle" to a rougher angle like 25 degrees and unchecking "Add detail to inflections" will make for a somewhat rougher looking display but also lighten up the density of the display meshes and that can help reduce memory consumption by quite a bit on more complex models.

But still it is somewhat doubtful that a huge 375 mb file will be able to be loaded all in one single chunk, you will still likely need to have it broken into a couple of pieces instead.

- Michael