If you look, via phpMyAdmin, at the table:
configuration
Do you have a record for the configuration_key when you search for configuration_key:
TEXT_PREFIX
If not, can you try adding this to your database:
Code:
INSERT INTO configuration (configuration_title, configuration_key, configuration_value, configuration_description, configuration_group_id, sort_order, last_modified, date_added, use_function, set_function) VALUES ('Text prefix', 'TEXT_PREFIX', 'txt_', 'Prefix used to differentiate between text option values and other option values', 0, NULL, now(), now(), NULL, NULL);
Does this fix the problem?
If you do already have a configuratin_key for:
TEXT_PREFIX
what do the values read on this record?