Kbase Article of the Week: iWeb: Menu Items are Unavailable After Reinstall →

Apple Support:

When iWeb is opened after a reinstall of the original disc, many of the menu items may be unavailable and new page creation may not be possible. Also the theme selection screen may not appear if there was no existing site in iWeb.

Note: These issues could occur if the iWeb software was updated prior to a reinstall using the original disc.

When you perform a reinstall from the disc, the original version of iWeb that shipped with the computer is installed, but the Receipts from the updated version of iWeb is still in place causing Software Update not to recognize that an update is needed. To resolve this issue, simply download and install the latest version of iWeb.