If guestbook is not fixable, try the feeback module.
You can overtaken the entries by a command like this in your phpmyadmin
INSERT INTO wb_mod_feedback (section_id, page_id,name,email,feedback,timestamp,comment)
SELECT section_id, page_id,name,email,message,posted_when,comment FROM wb_mod_guestbook;
The prefix wb_ is also your prefix? Ok, otherwise change it in the command twice.
Now the section_id should be changed before execute the command.
- install feedback module
- add a section feedback to the same page (remember the section_id e.g. SecId: [330] )
- change command:
INSERT INTO wb_mod_feedback (section_id, page_id,name,email,feedback,timestamp,comment)
SELECT 330, page_id,name,email,message,posted_when,comment FROM wb_mod_guestbook;
- execute command
Had tested this and it works for me. Without warranty.
It is only a try.