I've followed the instructions for including reCaptcha on a form (I got the form working properly without it first) but it won't work.

If I leave the reCaptcha fields empty I get the expected error (M27, M87, "Please enter the image characters"), which is fine.

If I deliberately enter incorrect reCaptcha information I get the expected error (M23, M132, "reCaptcha verification failed") which is also fine.

If I enter the correct reCaptcha information I *STILL* get an error. The error is show below...

An error occurred while processing the form [M23].
The staff at www.godfreyb.com have been alerted to the error [M24].
www.godfreyb.com apologizes for any inconvenience this error may have caused. [M26]

I also get an error email with the following information in it...

The following error occurred in FormMail [M18]:
Error=Failed to send email [M94]

Does anyone have any idea why the form works fine with the reCaptcha disabled but fails to send with it enabled?