CAPTCHA has stopped working

The CAPTCHA code no longer shows on our web site contact form; see url:

contactus.php

The form has worked perfectly and without problem for several months since I first implemented WebAssist Contact Form on our site. However, a couple of months ago we began having a problem with the CAPTCHA code showing up blank (no letters, just the grayed out "noise" background).

When I would reload the form from Dreamweaver to our shared hosting server, the CAPTCHA code on the contact form would work again for awhile. But now it has stopped working altogether, even when I reload the entire Contact Form folder. The form works properly, to include the CAPTCHA validation error message, all except the CAPTCHA. But without the CAPTCHA security code feature functioning properly, the contact form cannot be submitted.

Is there something our web hosting service may have modified on their server to have caused this to occur? I have made no other significant changes to our site or to the form that should have caused this problem.

Note that the GD Library (including FreeType) is installed and enabled on our shared hosting server, see url at:

phpinfo.php

Note that our WA_globals file is using the original CAPTCHA settings from the Contact Form Solution Pack per below:

$WAGLOBAL_Captcha_Width = "200" ;
$WAGLOBAL_Captcha_Height = "40" ;
$WAGLOBAL_Captcha_Characters = "5" ;
$WAGLOBAL_Captcha_Font = "Fonts/MOM_T___.TTF" ;
$WAGLOBAL_Captcha_BG = "ffffff" ;
$WAGLOBAL_Captcha_Noise = "000000" ;
$WAGLOBAL_Captcha_Text = "000000" ;
$WAGLOBAL_Captcha_BG_transparent = "0" ;