Google just imposed new URL VERIFICATION requirements for stores wishing to participate in Google Product Search listings.  We have posted the steps to verify your domain on your Google Merchant Center account.  Purchase this item if you would like help with this process.

Please provide the store URL you wish to validate.

For those who like to "do-it-yourself", here are the step-by-step instructions to claim your URL in Google Merchant Center:

1. You need to claim the URL that points to your store. Generally either http://www.mydomain.com or http://mydomain.com .
2. You must go to https://www.google.com/webmasters/tools/home and verify your url under your Google Account. Follow the directions outlined below:
   1. If your site isn't listed, click on "Add a site" and load the url. After adding it will go to the verify ownership page.
   2. If your site is already listed and verified you can skip these steps, if not verified click on the link on the right to verify.
   3. Select the Meta Tag verification Method and copy the meta tag provided.
   4. You must now add this meta tag to your home page and publish your store. You MIGHT be able to add to the head-tags variable (or override on the home page) depending on your store design and coding. Other stores may require the installation in a different location.
   5. After publishing you can return to Google Webmaster tools andclick on the Verify button.
3. After your site is verified, you can go back to your Google Merchant Center account, go to "Settings - General" under your store account and Claim the URL. Only one account can claim the URL.

Google posts more information at the following link:
http://www.google.com/support/merchants/bin/answer.py?hl=en_US&answer=176793

Exclusive Concepts has also posted a video of these instructions at http://www.exclusiveconcepts.com/blog/new-requirements-for-google-product-search-listings-wildcard-friday.html