The url I am using does not have two slashes (//) at the end and that is NOT what is causing the google map key error.
Here is how I am able to reproduce the errror:
1. Logged Off, open a link to a cache page (Like http://www.geocaching.com/seek/cache_detai...f-09e51705735b)
2. One the page has loaded log in by clicking the log in link in the upper right corner of the screen.
3. Once you return to the page the error is displayed.
This does not happen on all pages. When it does happen it may happens and I refresh the page it continues to happen until I close the browser and go back to the cache page. At this point the error does not display and never displays again.
I really think this is an issue with the key in the page for Google Maps. That is what the error message points to. It seems as if pages created on a development server with a different Google Map Key were moved to a production server and the Key didn't get updated. Yes, I am an IS Professional and I realize my geek is showing.
I have also consulted with others at my location and they usually do not get the error on the same page I do, So I have eliminated our office systems as the issue. I have also walked them through the procedure above on a page that resulted in the error and they also experienced the issue. I have also tried this at home with the same results.
Hope the additional information helps.