There are updated troubleshooting steps here.
There are some standard troubleshooting steps you can try, but as always, make sure you have backups before you try any troubleshooting steps.
- Restart Lightroom.
- Restart the Computer.
- Make sure you’re running the latest updates, both for Lightroom (by going to Help menu > Check for Updates) and also for your operating system.
- Optimize the Catalog.?Go to File menu > Optimize Catalog and wait for it to tell you it’s completed before moving on.
- Delete the Preferences file.?Close Lightroom and find the Preferences file. The Preferences may be in a hidden folder on some systems, which you may need to show. You could move or rename that Preferences file, rather than deleting, and if it doesn’t solve the problem, you can put it back. More instructions on that in the next question.
- If your catalog won’t open, check for a *.lock file alongside your catalog file, and delete it, and then try to restart. The lock file can get left behind if Lightroom crashes, preventing you from opening the catalog. If you find a *.lrcat-journal file, do not delete that, as it contains important information.
- Create a new catalog to rule out catalog corruption.?Restart Lightroom while holding down Ctrl (Windows) / Opt (Mac). Select Create New Catalog. Import some photos into that new catalog to check everything is working as expected. If this works, the problem is with the catalog, possibly corruption. (Don’t panic, that can usually be fixed!)
- Move all user presets to another location in case a corrupted preset is causing the problem. Corrupted fonts have also been known to cause problems.
- Update drivers on your machine, particularly the graphics card drivers.
- Damaged RAM can also cause some odd problems—Lightroom will find dodgy memory quicker than almost any other program. Run software such as Memtest to check your memory.