Does not work with WP 3.5

Sorry you had trouble.
I could not duplicate your problem. This version is tested working on WP 3.5

Check for theme or plugin conflict, because that had to be the cause.
Other login or anti spam plugins can break it.

@mike,
I had been using SI Captcha on 3 sites. All three of them have Genesis Framework with Child themes. The plugin was working great, but after upgrading those sites to WP 3.5, I was unable to login to anyone of them. I had to ftp and delete Si Captcha plugin.
I had not troubleshoot plugins and themes, but I assumed conflicts with WP 3.5 because after upgrade it stopped working. One of the site is a personal website with no plugins but Genesis Framework and it child theme Scribble.

The si-captcha upgrade failed for me as well. I am using WP 3.5 on Twenty-Eleven. The captcha image would not display. I had to remove the plugin manually. I tried re-installing the last version of si-captcha and it failed as well.

When that happens, there is no back door.

WP 3.5 on Twenty-Eleven or Twenty-Twelve works when I test it.

If it is not working for you, you must have a plugin conflict.

Here is how to troubleshoot which plugin is conflicting:
Look on the Admin – Plugins – menu.
Temporarily deactivate (not uninstall) all your other plugins. Leave this one still activated.
Does it work now? If yes, Activate the other plugins one by one to determine which one conflicts. Which one was it?

I have been working on this all day. It still could be a plugin conflict, be sure to test that first. but I do have a newer unreleased version you can test.
Contact me here if you can test it

I have been using this plugin for over a year now. Thank you very much for such a great plugin. I am also very happy to see that you have started to update the plugin.

@ssiddiqi1 and @sdpate48 it is working on all my blogs using WordPress 3.5. Like @mike suggest you must have a plugin conflict.

Kind regards

I released a new version 2.7.6.1 last night because I fixed some bugs and added settings for all the error messages. I also used completely different WP hooks for the login page. (my thinking is these hooks are less likely to interfere with other login plugins, but nothing can be for sure) Anybody who was having trouble with 2.7.6, try 2.7.6.1

If it is not working for you, you must test for a plugin conflict.

Here is how to troubleshoot which plugin is conflicting:
Look on the Admin – Plugins – menu.
Temporarily deactivate (not uninstall) all your other plugins. Leave this one still activated.
Does it work now? If yes, Activate the other plugins one by one to determine which one conflicts. Which one was it?

If you still have trouble I need to know:

What is the error or problem?
What steps to reproduce the problem?
Which form is it doing that on? login, comment, registration, or lostpassword
What version of WordPress?
What theme?
Are any other plugins causing it? (deactivate all the others to see if the problem goes away)

IF you have Jetpack v2.0.4. installed, downgrade it to v 2.0.2. Jetpack updates 2.0.3. and 2.0.4 broke several plugins, including SI Captcha, on my site.