Google Analytics error - _gat is undefined

The _gat is undefined error is effectively caused by a browser Javascript timeout. It often occurs with Internet Explorer 7.

Google has released new (asynchronous) code to replace the existing code snippet.

You can get the snippet here: Tracking Site Activity - Google Analytics - Google Code

Make a note of your UA- client number from your existing code, remove the existing code then put the new snippet in the section of your page.