Hello!
I haven't encountered an error like yours, so I'm not quite sure what to do, unfortunately...
Hopefully, someone with more experience with the editor can help you.
In regards to the MC2 editor resources you are requesting, I do know of one place that might help. It is a bit outdated, however, but most of the concepts explained should be the same.
I'll try finding it; I know it's somewhere out there on the Internet.
Does anyone else know of a MechLab website? It has/had loads of useful information on things like height maps, lighting, some scripting, water, fog effects, etc.