Problem with registration

Hello I am trying to make a new registration to my site www.comworld.gr and with th popup window I have those errors.

The name you entered is not valid.
The username you entered is not available. Please pick another username.
The passwords you entered do not match. Please enter your desired password in the password field and confirm your entry by entering it in the confirm password field.

although everything is ok.
and then it goes to a new windows to make registration and when I fill all the informations and press ok it says

Empty solution not allowed.

Can anyone help me?
Thanks

I don't this is problem with template but maybe with register form. Could you switch template to 'beez' and try to register ? Looks like your register is showing all possible errors from Joomla! when you try to create new user.

I am using gk_register and not joomla registration

Could you test this on default register page not with the pop-up ? Please just make new menu item with type "User registration".

it shows the same problem even when I use joomla registration. Do you know why can this happen?

It looks like you have some problem with ACL settings or some Joomla! core files are corrupted. My advise is to reinstall your site or recover from backup if you have some copies.

i have the same problem when i test this with the pop-up. But i don't have the problem when i test this on default register page (joomla registration).

how to resolve it?

Did you use reCaptcha ?

Did you use reCaptcha ?

Yes, i have used it on default register page (joomla registration).

Did you use reCaptcha ?

Thank you. I have solved this problem.

Could you share your solution with other members ? Where was the problem ? In reCaptcha configuration ?

Hi, I solved the problem following the steps below.
1.Go to Global Configuration >Site >Default Captcha - None Selected - >Save & Close button
2. Go to Users >User Manager >Options >Component Tab >Captcha - change to -None Selected or Use Default >Save & Close button

Enjoys!!!

Yes that is confusing in J! because there are two place to set captcha. If you need more help the reCaptcha configuration is described here >>How to use reCaptcha