CAPTCHA image is not big enough

[drmaves]

I'm using CF 8 and the <cfimage> CAPTCHA option. I am getting the following error message on a intermittent basis:

An invalid argument has caused this error.
Verify your inputs. The specified width for the CAPTCHA image is not big enough to fit the text. Minimum width: 311

By intermittent I mean that I can go to the page most of the time and it works fine but then once and a while I'll get the error. If I just refresh the page after getting the error it works fine.

The error indicates my minimum width is not large enough; however, I have no way to estimate this.

Anyone have any ideas?

Here's the code I am using:

[josheby]

Not sure if you still need help with this but the formula for calculating the minimum width of a captcha is as follows taken out of the CF8 CFML Reference on page 306.

"Note: For the CAPTCHA image to display, the width value must be greater than: fontSize times the number of characters specified in text times 1.08. In this example, the minimum width is 162."