I've had this "bug"(if it can be called such) happen twice now. The first time it mysteriously fixed itself(possibly?). And I never did figure out how/what/where/why. Then it happened again and was seemingly stuck that way permanently.
What am I talking about? It's a little hard to explain. Basically you can only view things in the editor "top down" and in "2D". By that I mean you lose an axis(or 2?) of camera movement. So the camera can only zoom in/out, and scroll side to side...sort of(but not really, it just spins around a selected a point, moving sort of side to side"ish"). The axis represented by the green line becomes non-functional(and the line itself can't be seen). Or maybe that's the only axis that is functional, and the red and blue are non-functional(I don't really understand what's going on with it)? At any rate, the ability to tilt the camera, and/or rotate it in any way, is gone. Which makes things nearly impossible to edit effectively. Hence, it renders the editor pretty much useless.
So what exactly is the problem? As you might expect, it's a camera issue. Specifically an error that gets saved in the ViewTerrain.xml(located in the AppData\Roaming\SpinTiresEditor folder). Which can be fixed by manually correcting a couple of values that have been changed and set to 0. Or just by deleting the .xml, and allowing the editor to recreate it. I'm not 100% sure how else to fix it(like I said, sometimes it fixes itself maybe? or maybe I fixed it another way without realizing how? I dunno for sure). I do know for sure that verifying the integrity of local files does not work.
What exactly is the error, and how do you correct it manually? Somehow 2 values in the Camera Dir= line get changed to 0. It takes two 0 values to cause the issue. So far as I can tell. I can only replicate the issue by changing the first and last, NOT the center, values to 0. Setting any non-0 value for either, or both, will not cause(or will fix) the problem. All 3 values set to 0 will cause an unrecoverable error when you try to open something in the editor.
<Camera Eye="(-2.607; 70.171; -47.312)" Dir="(0; -1; 0)" />
<Camera Eye="(-2.607; 70.171; -47.312)" Dir="(1; -1; 1)" />
How does it happen? I have a vague idea what caused it the last time it happened. No idea how it happened the first time. Anyway, somehow the camera got "lost" when I was viewing a map I'm working on. I think it got zoomed in or out way too far. The map suddenly disappeared from view(as if I'd accidentally zoomed in/out too far), and no amount of zooming in/out, or manipulating the camera any other which way, could bring it back into view. So I finally gave up and closed the editor. BAD IDEA!!! That broke it. The next time I opened it, it was stuck in "2D" mode...for good. Or so I thought...
Blah, blah, blah. That's the deal with it. And that's how you fix it. So when it happens to you, all you have to do now is google/search, find this thread, and not lose your mind trying to figure it out on your own.