Problem with ajax recommend

Hello,
I purchased ajax recommend and installed with success. The FIRST atempt to send an email was a success but after I couldn't use the module anymore. I always have this message: There was a problem with the request.
Well, I uninstalled the module and installed another time but the issue is the same.
Actually I'm building a joomla site in a subdirectory of principal website. However I don't think this is the problem (first attempt worked great)!

Thanks for your help.

Hi. I would have to take a look on the website so please send me the URL in a mail.