I have installed: Joomla 2.5.4 and K2 2.6.6
I have done the following instructions (based on Khalil and others)
1. Disabled the Captcha ReCaptcha Plugin
2. Set User Configuration - Captcha "None selected"
3. Set K2 Parameters for Comments to Enable reCaptcha in Comments to "Yes"
4. Copied and Pasted Keys to K2 Advanced Parameters
5. Disabled reCaptcha on Registration Form
6.Disabled StopForumSpam.com integration on the user registration form
7 Enabled the on the K2 Category the options K2 plugin and Comments

The comment form shows the generated keys by Google (see attachment), however when submitting the comment form results in a page hangup. Any tips and/or tips to debug?

Hello,

First of all you should upgrade to 2.5.11 asap. There are several security fixes.
I don't think you should have disabled the reCaptcha plugin and you haven't mentioned if you have any JS errors.

Hi Krikor, I have finally found the issue. Due to a mistake I made in the URL rewriting of the site URL, the K2 URL was not properly shown resulting in not executing the comments submit code correctly.

Thank you for your response.

The issue can be closed.

Regards,

Mark

ps. I have updated the side to the latest Joomla version