Went from LR 2 to LR 4. How long does LR 4 take to upgrade previews? I have about 4,000 RAW files from a Canon 40D. The status windows been stuck on upgrading previews for about ten hours. Is this normal or is it stuck? Specs: Mac Pro Dual 2.8GHz (quad core) 4GB RAM ATI 5770 GFX card Thanks!