I installed Windows 10 and after some time search in start menu stopped working. No matter what I typed in, the menu remained empty and the small dots going from left to right (search progress animation) just kept moving and nothing showed.
This is how to solve it: open Task manager (press CTRL + SHIFT + ESC), go to Details tab (If you don’t see it there then check Processes tab) and stop Cortana or SearchUI.exe. Just right click on the task then select End Task. After you end Cortana try searching again.