Ian, you can reset defaults by renaming your user folder (User/Library/Application Support/Vectorworks/2011. If you rename this folder and then restart Vectorworks, it will create a new user folder.
I have no idea if this will resolve your problem. However, once you have a new user folder, you can of course restore elements from the old one, such as workspaces and other saved settings.
There is no uninstall option for Vectorworks on either the PC or the Mac, so, yes, if you do decide to uninstall, drop the Vectorworks 2011 folder from the Applications folder into the trash.