Hi folks,
Thats weird,
I thought that seeing Vincent could not reproduce the problem that he may have been on a newer version.
I re downloaded the Beta and it was the same version.
Reinstalled and guess what ... Captcha works now

On my home server, so no doubt will work on my shared one.
Sorry Acylian, I should have done that.
The error was
Zenphoto v1.4.6-BETA[4196c58634e5dd718b0c2e551efc220b448f6a9d]
WARNING: str_pad() expects parameter 2 to be long, string given in C:\Program Files (x86)\Xampp\htdocs\zp-core\zp-extensions\zpCaptcha\c.php on line 18
str_pad called from c.php [18]
Not that it is relevant now

Thanks folks