It happens when I build my scene to standalone and Unity automatically reimport the assets. Then the models (rocks) with the CombineChildren (from the editor) attached just disappear when Play mode is on. ???
When I remove the CombineChildren script of that models, the problem is not present.
i have see this happen too when the newly combined model had more verts than fit in my graphics cards vertex buffer !
on most modern cards you can havearound 60.000 verts per object
but on shitty cards like those intel intergraded graphcis ones it can be as low as 16.000 !
your console should tell you something about this though ! can you post that here ?!
I can’t post that now, but my graphic card is a Geforce 8600 with 512 Mb of RAM and the objects don´t have so many verts.
If you have run OC this will occur when the parent of the meshes becomes occluded. If not…well…WTF??
HTH
BTH