AGuestbook commenting error?

Tried to search the forum, but found only couple of unanswered questions concerning this wannabe-bug.
When trying to addi a guestbook comment, I only get a blank page with header in it. Doesnt seem to matter whether the comment-password is on or off.
Is this a browser-related error (as in Opera 7.11, previewing a guestbook entry causes an error where user has to restart writing message), and has anyone found a solution to this one?

Could it be because that I, a no-talented newbie to PHP, have done some modifications to the Advanced Guestbook?
http://www.kokokuva.com/kirja.html for a preview of whats going on.

Great book, by the way, I've fallen in love with it after all them semi-working quarter-customisable perl-guestbooks.

-miika

Using advanced guestbook 2.2.

When someone posts a message and wants to review it, then make corrections...when they hit the "go back" button, the message is empty and they have to start over.

Also...when inserting a comment, you recieve an error message...making you think that the comment wasn't posted. Are these known bugs and does anyone have a fix for them?

Any help would be appreciated.

*BUMP*
Am I the only one with severe problems adding comments to guestbook?