NEC VT400 out of focus

Is it truly out of focus, or 'cloudy'? If it's just cloudy, usually dirty optics are the culprit. Removing and cleaning the lens and light path will probably remedy your problem. Cleaning the lens is not usually a big deal, but cleaning the light path is NOT for the faint-hearted. The light path is usually underneath all of the circuit boards, and requires complete disassembly for access. Also, there are lenses down there that require precise alignment for uniformity (no dark or light areas in the image.)