You are able to play at our server with the demo. However its definatly advised you get full version to work.
If you post your cfg from Quake 3 full version on the forum here I can take a look for you.
To find the Cfg go to your Quake folder, then a folder called baseq3, Then open a file called q3config.cfg in Notepad.
Copy the contents of their to the forum and we can take a loook for you ;)