If you start a new project just for poking around for example, and go to the TOOLS:Check LFM file in editor, you will get a window indicating there is a problem with 0 offset etc.
If you op to do nothing about it, exit in other words, then your now test program has no LFM file and all the work you just did is unusable.
I suppose saving the project may fix this, but I don't remember this happening and I really think this needs to be addressed wouldn't you say?
I do many simple test runs without actually saving the project, just use the temp folder that was assigned.
EDIT
I found that if you close the Empty LFM page from the editor, you can rebuild once again, however, if you attempt to read the LFM again, it comes with a different error.
Jamie