...the reason "Reset Ignored Updates" in my Software Update menu is unavailable ("grayed out") right now may be related to my entering my OS X sign-in password when my Genius requested me to.
I doubt that's the explanation; as I mentioned earlier, if you've never taken
the action called "ignoring" an update, there are no "ignored updates" to reset, and thus the menu command is dimmed.
As an aside, it's illuminating to see what the Apple Human Interface Guidelines have to say about the dimming of menu items. From
Apple Human Interface Guidelines: Menus (scroll down to
Naming Menu Items):
When a menu item is unavailable—because it doesn’t apply to the selected object or to the selected object in its current state, or because nothing is selected, for example—the item should appear dimmed (gray) in the menu and is not highlighted when the user moves the pointer over it.
