When ticket comes or on some events, the page throws error Contact your system admin. The Agent gets notification, and then on web browser the error comes. If I delete cache, rebuild config and restart Apache the error goes. The Folder /opt/otrs/var has 777 permission. I had installed and uninstalled ITSM module and the error comes. Apache Logs ------------------------------------------------------------------- The following log comes in apache. Fri Mar 15 15:12:07 2013] -e: Use of uninitialized value in concatenation (.) or string at /opt/otrs//Kernel/Output/HTML/DashboardCalendar.pm line 145. [Fri Mar 15 15:14:14 2013] -e: Use of uninitialized value in concatenation (.) or string at /opt/otrs/bin/cgi-bin/../../Kernel/Output/HTML/DashboardCalendar.pm line 145. ERROR: OTRS-CGI-10 Perl: 5.8.8 OS: linux Time: Fri Mar 15 15:15:16 2013 Message: Need TicketID! RemoteAddress: 10.115.1.54 RequestURI: /otrs/index.pl?Action=AgentTicketLock;Subaction=Unlock;TicketID=27;Challenge Token=cb759384ba97697d5bf1de0586140c97; Traceback (22573): Module: Kernel::System::Ticket::Event::NagiosAcknowledge::Run (v1.12) Line: 50 Module: Kernel::System::EventHandler::EventHandler (v1.17) Line: 245 Module: Kernel::System::Ticket::TicketLockSet (v1.587) Line: 3595 Module: Kernel::Modules::AgentTicketLock::Run (v1.19) Line: 106 Module: Kernel::System::Web::InterfaceAgent::Run (v1.73) Line: 866 Module: ModPerl::ROOT::ModPerl::Registry::opt_otrs_bin_cgi_2dbin_index_2epl::handler (unknown version) Line: 46 Module: (eval) (v1.94) Line: 204 Module: ModPerl::RegistryCooker::run (v1.94) Line: 204 Module: ModPerl::RegistryCooker::default_handler (v1.94) Line: 170 Module: ModPerl::Registry::handler (v1.99) Line: 31 [Fri Mar 15 15:16:15 2013] -e: Use of uninitialized value in concatenation (.) or string at /opt/otrs/bin/cgi-bin/../../Kernel/Output/HTML/DashboardCalendar.pm line 145. [Fri Mar 15 15:18:00 2013] [error] mkdir /opt/otrs/var/tmp/CacheFileStorable/CacheInternalQueue/7/1: Permission denied at /opt/otrs/bin/cgi-bin/../../Kernel/System/Cache/FileStorable.pm line 79.\n [Fri Mar 15 15:18:00 2013] [error] [client 10.115.1.54] client denied by server configuration: /opt/otrs/favicon.ico [Fri Mar 15 15:18:05 2013] [error] mkdir /opt/otrs/var/tmp/CacheFileStorable/CacheInternalTicket/5/b: Permission denied at /opt/otrs/bin/cgi-bin/../../Kernel/System/Cache/FileStorable.pm line 79.\n