Can not ad MSN Messenger to a message in EBR

EBR: 2.0.8.1
Joomla 1.5.25
website: www.seniorenchat.eu

Hi,
today I saw a new problem and I can't find a way to solve it so I try your help again
When I wanna add MSN Messenger to a message in the guestbook I can not send it and I get the error:

form is not complete. Fill in your emailadress.

Translated from Dutch in English by me so maybe the original errors is a little different? Well then I tryed to fill in MSN AND a regular emailadress, the same, then MSN, regular email, and put on "show emailadress"....still the same error.
Then I only put Name end homepage and only then I can send the message.
Can you please help me?

Greetings, Herman.

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