The 12/28 patch to upgrade the combat ability window and attack indicator was missing a file that was causing people to display a bugged combat ability window button or even crash out of EQ upon loading a character. This issue has been fixed and the correct zip with all of the files has been submitted here. You can ge them here as soon as it is available or they are ready now for your downloading pleasure at
http://sars.has.it. Sorry for the inconvenience and I promise to never upload a patch that late in the night again! Enjoy =)
-Sars