Ah, previously you said..
'Joomla 2.5 ABP 2.0.3'

I have never seen anything like that.
The text is not from ABPro, your server is responding to the AJAX validation call with that strange reply. The other AJAX calls seem to be working fine.
I really have no idea what is going on on your site.

You might try..
- remove the login widget from the bottom of the screen in case it is conflicting with the ABPro JavaScript.
- simplify the screen, un-publish all extras and UDFs

I followed your instructions and found the problem I had" ** 50% deposit required before work begins" this line was causing the problem I removed the" ** "and everything works correctly.
SOLVED
many thanks for your support
Keith

Cool. I did not know that would cause a problem.

Hi!

I just started to have the same message:

Not Acceptable

An appropriate representation of the requested resource /index.php could not be found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

--------------------------------------------------------------------------------

Apache/2.2.23 (Unix) mod_ssl/2.2.23 OpenSSL/0.9.8e-fips-rhel5 mod_bwlimited/1.4 Server at www.helseform.dk Port 80

I have the right download for joomla 2.5 and the it also worked the first week without any problems.

Suddenly yesterday this error started to pop up every time i press submit.

How do you think I can solve this one?

What has changed on your system?
Enabled SEO, changed server error reporting?

If using a 3rd party SEO plug-in ensure it is told to ignore ABPro.
Ensure your Joomla Error Reporting is set to 'System Default', Global Configuration screen, Server tab.

Hi again!

I asked the hosting company if they could think of what causes this. They just wrote back that they have made some corrections and now it works again. I think they have made some adjustments that causes the error. But it is up running again & I dont know what the problem was.