have you tried to run the RatzED with admin permissions?

Hello!
The last update fixed some importer bugs. Please try to re-import the meshes.

Or test in a new empty map with the meshes imported and placed, if it renders then.

I just looked at your map : ).
If you create such a big map and just use custom meshes then you should reduce the "Cube Lightmap Resolution" by a lot. A lot of rendertime is used on those big cubes.
On the other side the custom meshes need a much bigger lightmap. If you click any mesh you can disable the "auto lightmap size" and set that to 1000-2000.
Also the ground mesh has a very bad uv2.

When i played it there wasn't any playerstart object in the scene. It actually should not be possible to upload a map without any playerstarts but it seems like that's the case here.

Originally posted by snowflake:

Thank you, I fixed it! (made it all over again, actually haha)
Another question - why does it replace all of my meshes when i re-start it? For example, if I have two meshes called Cube_002, it will replace all of them with the one I've imported last. Is there any way to replace them back, all at once?

Edit: Figured it out! Any way to move the camera faster around the map? The current speed is very slow and I dont know how to make it faster.

You can move faster on the editor by holding ALT + left mouse button for aim, then hold ALT + Right mouse button for super zoom (moving mouse to the left/right - zoom in/zoom out, i use this method for moving around large maps