Ran across this tonight. Someone had entered a prefix-list with the name “at& ;t” instead of “at&t” (wordpress didn’t like it either so I added the space between the p and the ; but they should really be together.
Oddly enough, IOS wouldn’t allow the bad line to simply be deleted. The “;” had to be removed so that the no command included “at&t”
Probably some sort of a regex problem or an ascii escape character but it’s still kind of strange.