Have you checked your graphic card, and Java, try to check if you have all up to date, also please do the Java medic test here:
http://pirategalaxy.com/support/medic
Are you trying to play by browser or have you downloaded the game client, that works best.
On PG website, http://pirategalaxy.com you can download it.
If you use the client, uninstall it and re-install.
If nothing works, please file a ticket, give a clear description of your issue
Read here for instructions:
http://forum.pirategalaxy.com/viewtopic.php?f=253&t=14998