As of December 5th, 2003, (build 10506), this message is a special case of the more general message that a token could not be found, and occurs if a character that was slated for special formatting, cannot be found at the end of the text part of token conversion of a textbox, and just before it starts to apply attributes.
Before build 18365 (October 29, 2017), this message was almost always due to the use of a holidays symbol filter (or of the no duplicates options) and informed you of the symbols that had been removed by filtering or the use of the no duplicates option.
However, since build 18365 (October 29, 2017), the Filter or No Duplicates holiday symbols display options should no longer cause this message to be generated spuriously.
Any appearance of this message should therefore be taken more seriously.
Topic 176240, last updated on 19-Apr-2020