It seems that at some point my KDE installation stopped seeing the Alt+F1 combination as a link to the Meta key, as pressing my Meta key by itself to open the launcher widget or perform any other action no longer works. Instead I have to actually press the Alt and F1 keys to achieve what the Meta key should do. I tried binding it from each widget's settings window, from the Shortcuts section of System Settings and finally from the kglobalshortcutrc text file itself; it didn't make a difference.