I've seen this error when running worldserver through an IDE and not setting the working directory. I would imagine you might see it as well if you were to try running the executable from anywhere but the bin folder. For example if you try to run it from /home/wowrp using the command ./server/bin/worldserver. If you are in fact running it from the correct location you can just set the full path (/home/wowrp/server/data instead of ../data) in your config file to get around it.