Most likely the host has upgraded the PHP installation. create a new file named PHPinfo.php and add the following:
<?php phpinfo(); ?>
this will show information about the php installation.
Look for the section Titled "GD" and make sure that True Type support is enabled.
If it is enabled, try changing the path to the font file in the WA_Globals.php file:
$WAGLOBAL_Captcha_Font = "Fonts/MOM_T___.TTF" ;
to a site relive path:
$WAGLOBAL_Captcha_Font = "/ContactForm102/ContactForm_GMC/WA_ValidationToolkit/Fonts/MOM_T___.TTF";