I have a catalog on an external drive that was originally created in Lightroom 4. I had Lightroom create all the 1:1 previews. This was Novemeber of last year. Now I have Lightroom 5 and have upgraded the catalog. The problem is in the Library module when I zoom 1:1 it sys loading and never stops. It also never seems to calculate the histogram. If I switch to the develop module it loads fine. Any ideas on how to fix this?