Regardless of the reason, do not bad mouth your current employer. Negativism will always hurt you. Good answers include: "There is no room for growth at my current employer. I am looking for a company with long term growth opportunities". "Due to a company restructuring, my entire department is relocating to Florida. I was give the option of moving, but do not wish to relocate". "My current company is not doing well, and has been laying off employees. There is no job security there, and more layoffs are expected".