I see that you've spend great amount of time on creating "environment" for captcha like reloading and so on, but you actually forgot about captcha itself, and the fact that soon it is 2012, not 2000 year.
Any most stupidest captcha cracking script will crack your captcha in no time!
And here's why:
1. only 15 chars!(16(hex)-1(because 0 is being stripped)).
2. SAME bold font every time.
3. text is always in straight line.
4. background always is a single colour, not an image.
5. ONE word which is ALWAYS 5 chars in length.
6. chars have same spacing between each over.
captcha is designed to prevent spam/bots not to demonstrate amazing image reloading skills, Fox captcha fails to meet its purpose of life and so it is useless.
Said Bakr - 2011-09-01 01:17:38 - In reply to message 1 from Ignas
Thank you for your valuable comment. I'd like to mention about the fixed number of characters which they are chosen from 15 characters set, the characters are lateral adjacent to each other, so it is optically form more complexed patterns more than the 15 separated. In other word, it may acts as Chinese writing for any OCR. Another thing, don't forget lines and the number of characters may be more than 5 too.
Another thing, I tried to keep the captcha image easy to catch for the human eye avoiding some hill reading that may appeared in some other captchas.
If it possible, I ask you to supply me with any resource or tool that allow us to check Fox_captcha against OCR.