Main photo in develop module does not show current adjustments

I've been using Lightroom 4 for many years with no problem but right now the photo I am working on does not show the changes I am making to it until I click on the navigator area and click on fit or fill or something to change the lage image-then it shows what I have done recently. The thumbnail in the navigator area does show what is happening in currrent time, though. So in review, while I make adjust ments with the different tools, nothing is showing up as changed until I click on fit or fill or something and that somehow "refreshes" the large image and then its up to date on the current workflow. What to do??