Hi Kurt
Your souce code shows the following path:
<div class="fieldGroup"> <img src="WA_ValidationToolkit/WAVT_CaptchaSecurityImages.php?field=Nehmen_Sie_Kontakt_auf_group_Sicherheitscode&font=Fonts/MOM_T___.TTF" alt="Security Code" class="Captcha" /> </div>
If I try to download that file I get a file not found error. Try to upload the font to that path, too and see if it works ---> Fonts/MOM_T___.TTF
Or change the path to WA_ValidationToolkit/Fonts/MOM_T___.TTF