Lightoom 5 crashes when you rate, label, or flag your images.
Replace the current ui.dll file with the new one below.
Note: make sure you install the appropriate file into the appropriate version of your operating system.
To replace the old ui.dll file with the new one:
1. Open Lightroom 5.
2. In Lightroom, choose Help > System info.
3. Write down the data under Application architecture (x64 or x86). This is the version of Windows you're using.
4. Write down the Application folder name. This is where Lightroom 5 is installed.
5. Exit Lightroom 5.
6. If your Application architecture was x64, click on the x64.zip link below.
Windows 64-bit ui.dll
8. After the file is downloaded, double-click on it to unzip it. Select a folder location that you'll remember, such as the Desktop.
9. Open the folder in Windows Explorer where Lightroom is installed (Step 4).
10. Rename the ui.dll file in that folder to ui.dll.old, for a back up.
11. Copy the ui.dll you downloaded to the folder Lightroom is installed in.