Your problem is very simple to fix. your normals are reversed. You can easily see which faces are pointing inward by enabling Backface Culling. This enables you to see though the back of faces like you do when you press P. You could also enter edit mode on that object, and enable the normals ...

I am using the Mirror Modifier to try to make a cinder block mesh. It is composed of some curves converted to meshes and some manually assembled faces. It appears to be having trouble with overlapping faces, although I cannot see a reason for that to be happening. I have tried extruding the face...

As stated in Answering vague support questions (once)?, we should consider having some "canonical posts" for some hardware posts. Some examples of topics which might benefit from a canonical post: Problems enabling GPU for cycles: We get a large number of questions asking about enabling cycles...

This is a place to keep track of and categorize good questions or answers which may be helpful to refer to at a later time, a kind of general Blender reference index. If you find a post which you think belongs here feel free to add it to the corresponding answer. Please keep a few things in min...

Update: Since this post is less likely to be seen by visitors to the site and is technically not what meta is for (we were working on the kinks at the time), there is now a community maintained wiki post on the main site listing many resources for blender. If you want to contribute to this, add ...