I vaguely remember getting that error once. I'm not sure I remember what I did to fix it.
Make sure your eq client is updated. make sure you are using the latest version of the emulator and database. Shut down any unnecessary applications. Make sure your Video card drivers are current. Also; can you play on the live servers,
can you play on any of the 'green' eqemu servers?
It would be easier to help if you posted more info. Follow this link and post the appropriate info next time.
Read This and Post your Info.