3-4 Second pause when selecting objects.

In my current project (and my first) when ever I select an object their is a 3-4 second pause before blender will recognize the command, and during that short time blender does not respond either, like a little freeze. However, it doesn’t happen in new files, which work fine, or in other modes.

Your scene is probably too complex, try using layers, and hiding objects you’re not working with.