[otrs] OTRS perl script madness

I'm seeing some very strange behavior from my installation of otrs 2.1.5. The wrong screens load intermittently. So for example I will click on the link to: http://88.191.14.190/otrs/index.pl?Action=AgentPreferences And instead of seeing the preferences screen, I get either the current screen to reload or another, apparently random, screen to appear! This happened in the midst of trying to sort out problems with mod_perl and 500 script errors. I've changed the apache.conf file and tried different settings, but I haven't actually touched otrs config files very much at all. Can anyone help me?