Something odd happened a couple days ago. After working great for a while, it suddenly stopped again. During the same LabVIEW session, no less. Just now I ran LabVIEW and the shortcut works normally again. Something is happening that is invalidating the shortcut, or redirecting it to nowhere.
I did try repeatedly pressing Shift, Ctrl, and Alt after the shortcut stopped working, to see if I could get Sticky Keys to come up, but no amount of presses did anything.
Finally, I think LabVIEW crashed as it closed, which has been happening a bit lately. I'll see if I can pinpoint the cause of the crash, and see if it could be related.