What update was that? What version of Audacity are you using (all three numbers)?
What version of Windows are you using?
Try deleting the “EQCurves.xml” file at Users<your user name>\AppData\Roaming\Audacity\ . If you are still on Windows XP, that file is at Documents and Settings<your user name>\Application Data\Audacity.
If you don’t see the AppData folder, type or paste the following into the file Explorer address bar then press ENTER:
Providing you have not deleted XML files yourself, you should still be able to use the default EQ curves shipped with Audacity after deleting the file suggested.