No dialog box and in fact no video out from what I can tell. In one case I was playing World of Tanks, pressed escape to go back to the garage boom - black screen. Couldn't alt-tab or cntrl-alt-del and not a monitor problem (although this monitor is pretty old). Edited to add: yes stock clocks.
Getting system freezes as well now too. Doing virus scans just in case but have had zero problems with this box until installing the new Geofrce Experience and the new nvidia drivers. Alternative theory - PSU or mobo going south. Going to replace the psu Monday with one of my backup PSUs. Third theory - do a complete wipe of the graphics drivers and do a re-install (something I haven't had to do for ages).
I have nothing against humanity that thousands of years of nuclear winter won't take care of.