I need to run a bunch of viewsheds that are going to take some time to compute. I'd like to set them up so that they will run sequentially overnight. I figured that the best way to do this was with ModelBuilder. Now I've never used this before, but I read some tutorials, watched ESRI's video on Youtube, and what I am trying to do is very simple. And this is the error I get when I try to run my test model. It gives me the little yellow "I'm ready to go!" shading, but then breaks immediately. I haven't even added a second process, and I'm not quite sure how, but that's a problem for later.
I'm baffled. When I turn and run the exact same process through the geoprocessing tab, it works just fine. My data is not the problem here. I probably made some very elementary mistake here. Does anyone know what might be wrong?