Hi Ken,
This error is likely do to a Google Apps domain migration on the account you
used in the clientEmails field:
http://adwords.google.com/support/aw/bin/answer.py?hl=en&answer=188607
Have the user log into their account, complete the migration, and then log
into the AdWords web interface.
I've just started running into failures with some calls to the report API.
These calls just started failing yesterday (7/21/2011). Previously they
worked daily for the last few months.
Any idea what's up?
Here's the XML (request and response - with the email and tokens removed):
QueryREMOVED20