Well troubleshooting is a skill and like any other it gets better with practice. It took me awhile to figure this one out. So........ Every monitor has a unique ID which Windows reads and remembers when you plug the monitor in. (Any driver developers out there, I'd really like to understand exactly how this works and where the ID database is.) So when you plug the monitor in, if the monitor's ID is not in its database, Windows records the ID and sets the monitor to its default settings. Well that's great if you don't mind squinting at 1920 x 1080 on a 24" monitor. But about half our users ask me for something larger, and I like to keep my users happy. But unlike previous versions of Windows which did a pretty good job of only presenting resolutions that fit the monitor, Windows 10 throws everything at you and lets you figure it out. Is it 1360 x 768 or 1366 x 768? Y'mean to tell me I got a 3.4 GHz processor here, and I gotta pull out a calculator to check the display resolution?!?! Windows can't figure this out and highlight the correct ones? You gotta be kidding me. Well for most wide screen monitors, the resolution is a 16:9 ratio. 9th grade algebra. Cross multiply: 16 * 768 / 9. It's 1366. Set it to 1360 ... oops, 6 pixels off, easy mistake to make ... and Windows doesn't complain. But due to a bug in the driver, when you sign out... the screen goes blank and stays that way. Plugging a "good" monitor into a "bad" system fixes the problem? Yes. Hint #1, explanation above. Plugging a "bad" monitor into a "good" system, problem follows the monitor? Nope. Again, hint #1. It's never seen the monitor before, it sets it to default settings. This really threw me, but once it sunk in, the answer was obvious: What did the bad PC's have in common? Settings were changed from the default to an incorrect value. Only those PC's with 1360 had the problem.About 5 in all. Changed it to 1366 - it didn't stall. ta da. problem solved.    
Hi, We have several Optiplex 7050's with the same problem: They stall on Sign Out and Switch User. That is to say, when you click on Start / Sign Out, instead of going back to the Windows 10 welcome screen so you can sign in again, the screen goes blank, completely black. The monitor says it is not picking up a video signal (Display Port connection). The system becomes nonresponsive. The disk activity light goes into a slow blink pattern (like 1 blink every 1 or 2 seconds). The Power Button light remains steady blue, no error indicators. The only way out is to press and hold the power button and shut it down. A Restart works just fine, just Sign Out and Switch User are affected. Windows 10 21H1 (19043), all Windows Updates applied. Both sfc /scannow and dism /online /cleanup-image /scanhealth are clean. Drivers are all up to date, updated with Dell Command Update. The PC is under warranty, but Dell tech support wants us to reinstall Windows. I prefer the rifle over the shotgun approach. Can someone please assist in troubleshooting this problem? Thanks in advance,Dan    
Optiplex 7050 stalls on Sign Out and Switch User