I'll not be able to fix the shader, most likely, but I'll have to find out what's causing this. Thanks for the report! Let me know if it happens again :)

A little update on this - If undo were to be implemented, SF would also move up to 4.3 as minimum Unity version. 4.3 switched to a new Undo system, and deprecated the old system. I'd rather keep SF striving to stay up-to-date rather than backwards compatible.

Make a new topic on it and we'll see if it gets implemented :)
Edit: Actually, vote on this instead: http://shaderforge.userecho.com/topic/254089-preview-background-texture/

It seems all meshes might have imported with a scale of 0.01, so the preview mesh was simply too small to be seen.

1. Search for sf_meshes in the project browser. (ShaderForge/Editor/Resources/Meshes/sf_meshes.fbx)
2. Select it and set its import scale to 1 instead of 0.01

It seems all meshes might have imported with a scale of 0.01, so the preview mesh was simply too small to be seen.

1. Search for sf_meshes in the project browser. (ShaderForge/Editor/Resources/Meshes/sf_meshes.fbx)
2. Select it and set its import scale to 1 instead of 0.01

The scale is per-asset, not globally, like Wesley said! I'm fairly sure this was the issue, so I'll make this as finished :)