I've tried using the following to replace certain strings and am getting no affected rows, even though I know the strings exist. The only thing I can think of is that some chars need escaping:

UPDATE text_table SET text_string = REPLACE (text_string, '=D>', '=D)');
UPDATE text_table SET text_string = REPLACE (text_string, '[-o<', '[-o{');
UPDATE text_table SET text_string = REPLACE (text_string, '<<(:', '{{(:');
UPDATE text_table SET text_string = REPLACE (text_string, ':>((:', ':}((:');
UPDATE text_table SET text_string = REPLACE (text_string, ':>:-)', ':}:-)');
UPDATE text_table SET text_string = REPLACE (text_string, '>:->', '}:-}');
UPDATE text_table SET text_string = REPLACE (text_string, '::-<<:', '::-{{:');
UPDATE text_table SET text_string = REPLACE (text_string, '>:-(', '}:-(');