Hey, thanks, guys! You're right - Tools|Options|Search|"Match Whole Word" is the setting attached to the macro. For whatever reason, it was stuck "on", and re-applying the macro wouldn't toggle the setting. I was able, however, to manually change the setting via the GUI and turn off Match Whole Word.
Better still, once I did that, my Toggle Whole Word key appears to be working fine again, and it does in fact toggle the setting.
Now I know how to un-stick it should it get stuck again.
Thanks again!