I have the same problem. I cannot use Windows File Explorer Search. There is no way I can put the cursor in the Search box. Restarting Windows File Explorer has no effect. It all started after I allowed Windows to apply updates.
I've said it before - Microsoft is in over its head with these problems. In their efforts at constantly untested and buggy updates on users that aren't wanted and give nothing but problems, they've lost any understanding of what is important to users. If that wasn't the case, we'd be able to opt for the Classic Desktop we all know how to maneuver around to get things done. I see my PC as a tool. Windows XP worked great for that task. I didn't have to make any modifications to it to get my tasks done in a timely manner. It just worked! Now they're killing the best replacement since then in the form of Windows 7. With every update, there comes a major problem we users have to deal with and what is the response from Microsoft? There is none! We're left to flail about on our own hoping a 3rd party with a thorough understanding of the problem can give us a fix or work around.
Not being able to use search sucks!
Group by Date sucks!
Microsoft why are you doing this to your users?