No display of entries in Advanced Guestbook

I installed Advanced Guestbook and everything is working, but when someone post an new entry, the enrty isn't displayed on the screen. I do get the message "your entry was added succesfully" but the text of the entry isn't displayed...
The name, homepage etc. are displayed, but the comment isn't.
I looked in MySQL and the entries are visible in the table book_data so there is no problem there.
Someone got an idea what I can do to fix this?

Thanx in advance.

Don’t get my wrong, but are you sure you haven’t set the font color the same as the background.
If not do you have a link?

Nope, background color=white and font color=black so that's not it.
The link is:
http://www.tvse.nl/site/guestbook/index.php

If I look in the source code then I don’t see the messages either.
Maybe one of the php files is damaged, but I don’t know which one.
Did you change anything?

Haven't changed a thing, only the config.inc for MySQL connection. I don't think a .php file is damaged, I tested the guestbook on my own computer (Apache server) and it worked fine.