mysterious captcha error msg

[rrhobbs]

I am getting some intermittent mysterious captcha error mesages on my contact page http://rrhobbs.com/location/phMailer.php.

It's a customised version that I paid Scott a donation for and customised further with some simple html.

What is really wierd is in making changes to the file I rename the old one, and ftp the new file to the server, and get the error. however, if I open the old file, it works- here is an example that worked for me: http://rrhobbs.com/location/phMailer.php.test

Also I open one or the other just fine in Firefox, but get the error in IE. or vice versa. after clearing the cache and reopening the browser.

????