Redmine

Hi Guys,

everything is working great, the svn, adding issues, adding wiki, forum, adding files in the files section you name it, including plugins.
but one thing is not working out:

when you go to new issue or update an issue and want to attach a file (in exmpl. screenshot)
we get error 500.

details about the system:

Redmine 0.8.2.stable.2598 (MySQL)
Default administrator account changed True
Attachments directory writable (/var/www/redmine/files) True
Plugin assets directory writable (/var/www/redmine/public/plugin_assets) True
RMagick available (optional) True

Running Apache with mod_rails.

can't see any permission issue or something inside the production log.

any assistance would be great, we are breaking our heads here.

thanks in advance.