Google have recently updated their documentation for using a single API key under multiple domains - see also this thread http://drupal.org/node/818638. I switched my setting in the Google control panel from simply:

mydomain.com

...to the recommended:

*.mydomain.com
*.mydomain.com/*

...but when entered into Keys, this triggered "Key for 'google_maps' @ '[my domain and page]' doesn't exist."

However, if I revert to only one domain in Keys, it starts working again. I tried both comma and comma-space as delimiters for the Rule field. It looks like either Keys doesn't like the wildcards or doesn't accept more than one domain.

I'm using:

  • GMap 6.x-1.1
  • Location 6.x-3.x-dev
  • Keys 6.x-2.1