I'd have to see the large file to know... Can you attach it?
If you send me your copy of: wavt_captchasecurityimages.php then I can fix the problem and send it back to you.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.