Question 500 Internal Server Error when trying to add a topic

I have Joomla version 1.5.18 and Kunena version 1.5.12 running on www.dominickirwan.com .

Every time ANY (admin as well) user tries to create a new topic on the Kunena board I get the attached error message with an internal server error.

The comments are set for review and the forums are moderated but I have switched all these optiont to no avail.

Can anyone help me please?

plz demo user

www.dominickirwan.com/index.php?option=com_kunena&Itemid=175

Username: demo
Password: demo

Many thanks.

try to change to default template

you made some change there ?

you edit also language file

I didn't edit any language file.

I changed the template back to the original one, but the problem still exists.

500 Internal Server Errors usually result from bad PHP code. There's something on the page when you're trying to add a new topic that is causing the PHP interpreter to object. One way to find out the cause is to enable Joomla debug mode and look at what is being reported.

Searching for 500 Internal Server Error at this website might also give you a few clues, too.

My guess is that another module (not Kunena) on the site is causing the problem.

docs.kunena.com/index.php/Conflicting_plugins
disable css js compress plugin

sozzled

I apologies but I did already search the forums. There seems to be plenty of instances where this happens but very few solutions.

When I enable Joomla debug mode there is no error reported on the error page.
My cpanel error log only reports:

[Tue Jul 13 08:46:08 2010] [error] [client 82.7.104.189] File does not exist: /home/dominick/public_html/favicon.ico
[Tue Jul 13 08:46:04 2010] [error] [client 82.7.104.189] File does not exist: /home/dominick/public_html/500.shtml, referer: www.dominickirwan.com/index.php?option=c...func=showcat&catid=4


etusha

I dont have a css js compress plugin. At least I don't think I do.

yes you have
<link rel="stylesheet" href="/media/system/css/css-d88325c26fccffc16fdcbe6895c17519.php" type="text/css" />


<link rel="stylesheet" href="/plugins/system/rokbox/themes/light/css-b518d664167dd795248190ff44b8159f.php" type="text/css" />


<link rel="stylesheet" href="/templates/rt_iridium_j15/css/css-68d2be5c945ee913eaca624baff6ccc5.php" type="text/css" />


<link rel="stylesheet" href="/templates/system/css/css-068042e5faad58e5ca9b950e5e62bcdf.php" type="text/css" />


<script type="text/javascript" src="/cache/js-9a8eaa6ee36838127f259b43edd78cd5.php"></script>

Ah, I think the plugin is System - RokGZipper,

which I have now disabled as well, but same problem.