Saving the objects to a new group like you said might solve the problem. It's simple to do. Just go into the Object Maker and type in the .MESH file name and texture into the appropriate boxes. On the first tab there are boxes for an Object Name and Object Group. Name your object whatever you like and then type a name in for a group. Click save and that will automatically create a new group. Then, if you wish to add more objects to that group simply repeat the same steps with another mesh, making sure to type in the same group name as you did before. I know you said you really didn't want to do this, but i may help to solve future issues.
If in fact that is too much trouble, you may want to try exporting your map first before entering it in game. Sometimes before exporting, the map won't always show objects when you go into game. Hope this helps.