In need of advice on Text_CAPTCHA

Does anyone have experience using Text_CAPTCHA who can help me diagnose what I hope is a simple problem? Any help or advice or direction is much appreciated. I just installed Text_CAPTCHA and tried to run a test, just to be sure I can get an image and matching string. After calling (all of this is straight from the sample code provided): $c = Text_CAPTCHA::factory('Image'); $c->init(200, 80); This: $phrase = $c->getPhrase(); works fine and returns a string. This, however: $im = $c->getCAPTCHA(); returns nothing - just an empty string. I tried it also with getCAPTCHAAsPNG() and getCAPTCHAAsJPEG() with the same results. I also tried with: file_put_contents('test.png', $c->getCAPTCHAAsPNG()); (and AsJPEG) with the same result - an empty string and an empty file (it gets created, but has zero bytes in it). I've reviewed the code in all of the Text_CAPTCHA and dependent classes and can't seem to see anything (though this may be inexperience...) Can anyone help point me in the right direction to get this working? Thank you very much! -Jeff