@gata said:

A windows update may have done something to your video driver. Reinstall your video driver/look for an update while you're at it.

You know, that might be it. I recently updated the drivers manually while checking to see if anything new was out. I updated on or about 1.25.08, which could be the culprit.

Maybe I can roll it back and see if anything happens...

Have a look at the SketchUp Basecamp video "Working With Terrain and Other Irregular Surfaces" that Daniel Tal gave. http://sites.google.com/site/3dbasecamp2008/.
Another on would be "SketchUp and AutoCAD" Mitchel Stangl and Daniel Tal

Hope it helps.