writing captcha image file

[amaltasb at gmail.com]

I have a script which generates captcha file on
/usr/local/apache/htdocs/captcha directory. The script is working fine
when i execute it from terminal>
>/usr/local/bin/python generateCaptcha.cgi > and it writes to /htdocs/captcha directory

but when I execute the script through
http://www.mydomain.com/cgi-bin/generateCaptcha.cgi its failing at
im.save(file_name, 'JPEG')

I changed the permissions to 755.

Can anyone help me...

Thanks