Well, I can't explain this, but here's what I did to correct problem. I was using OpenLP portable on a thumb drive. I formatted a second thumb drive & copied the entire OpenLP folder from the original drive I was using to the new thumb drive, and it ran perfectly from the new thumb drive. I re-formatted the original thumb drive, copied the OpenLP folder from the new drive back to the original one, and it ran perfectly. Wierd, huh?