The 500 error does not appear all the time, now it shows the post list, but only parts of it and without any format. Look second screenshot

Hello Joachim,

Is it possible for you to provide us with the back end and FTP access to your site to check on this issue? You may store your site access at http://stackideas.com/dashboard/site so you don't have to provide these information all the time

I put Access Data in Hidden Area. ;-)

it seems like you didn't provide us with your Joomla backend access, can you update again on your first post?

I provided you with BACKEND access data AND FTP Access data in hidden area.
The problem is, that this data seems not to be stored.
Next time I open the hidden area, infos are not available.
So there seems to be a big bug in your support system here.

I will put now the data again in the comment field in hidden area.

Now I tried to open the list, to delete my test posting, but is not possible!!!
Please solve this ASAP. Tests posting on our website is BAD for USERS and irritates!!!

I provided you with BACKEND access data AND FTP Access data in hidden area.
The problem is, that this data seems not to be stored.
Next time I open the hidden area, infos are not available.
So there seems to be a big bug in your support system here.

It seems like I was unable to replicate this issue, i can update your Joomla backend details into your previous post.

Now I tried to open the list, to delete my test posting, but is not possible!!!
Please solve this ASAP. Tests posting on our website is BAD for USERS and irritates!!!

I would always encourage our user start a new thread regarding with their new question/issue, so you will be get faster response from our moderators who working on. By the way, the reason why you hitting this is because you set your "default list limit" to 500 so your current PHP memory limit unable to afford show 500 article at the same page, i already help you reduce it display 20 per page, it should work fine now.