I recently read a blog post that lists several steps you can take to solve problems with Lightroom. These helpful suggestions were posted by Victoria Brampton, aka The Lightroom Queen, on her blog.
- Reboot Lightroom, and possibly your computer.
- Optimize the Lightroom catalog.
- Check for updates to Lightroom, any drivers for your monitor or graphics card and system updates as well.
- Reset Lightroom's preferences. Now there's a keyboard shortcut to accomplish this: on Windows hold Alt+Shift and start Lightroom; on Mac hold Option+Shift and start Lightroom.
- Test Lightroom by creating a new catalog. (This is ONLY a test.)
- Rule out corrupted presets and fonts.
- Try a clean user account.
- Check for hardware & operating system problems.
- Ask for help on the Lightroom forums: www.Lightroomforums.net