Happened again last night. Opened my project and the CV was on top, how I left it. Clicked Alt+1 (using the keyboard 1, not the numeric keypad 1) and nothing happened after a number of attempts. Using the mouse, I selected View | Track View from the menu; nothing, CV still on top. Clicked the CV dock X and the CV was dismissed and the TV was exposed. Now Alt+2 and Alt+1 work as expected, alternating between CV and TV respectively.
I think there must be something I'm not getting about the interaction of the dock and Alt+1 and Alt+2. There's a precedence there?