Blank page when trying to post a comment

Hi,

I have set up a new wordpress blog.

When i try to post a new comment i get a blank page with no error or anything else.

Searching through the web i found helpful things like “deactivate all plugins” and “try another theme”. What i did but i didn’t help.

What is wrong here? My other blog is running perfectly (same server what means same system settings just another database connection)

Thanks

PS: Yes i can write new postings 😉