I encountered same problem as you - firstly got locked out of admin by TBT enhanced grid extension which l later fixed.
Also found that l couldn\’t access Google API and received the same error message as you.
I read this thread here http://www.magentocommerce.com/boards/viewthread/18073/ mentioning that \"Google API was trying to retrieve a shipping method that was not available any more\”.
I realised that after upgrading to v126.96.36.199 my Mage_All.xml file had been overwritten. I had altered my previous Mage_All.xml file to include reference to a shipping extension that l had customised which was saved in my app/code/local directory.
After adding in the reference to my customised shipping extension in the v188.8.131.52 Mage_All.xml file, l am now able to access Google API.
So l think it is shipping extension related. Hope this helps.