So all of a sudden, after a week of using it, I get an error message on my zabbix server
gui (http://localhost/zabbix/.)
The error says: Zabbix serve
I was in the same trouble. For my case, that was a conflict between /etc/zabbix/zabbix_agentd.conf and zabbix_server.conf parameters. I adjusted
"DBHost=localhost",
"DBName=zabbix",
"DBUser=zabbix",
"DBPassword=******",
"DebugLevel=3"
"ListenPort".
If you run the default installation, you should keep ListenPort=10051 for the server and 10050 for the agent.
Cheers!