Forum:SH:The modification you tried to make was aborted by an extension hook

I'm trying to make a simple spelling correction and save changes, but I keep getting the following message when I attempt to save: "The modification you tried to make was aborted by an extension hook". I'm literally adding a single letter (changing "on" to "one")' so I can't imagine this would be a violation of any editing rules. Any idea why this might be happening? Thanks.