I've tried using a different Google account (to see if it was account-specific), but it didn't fix the problem.

I've had a look at the Latitude OAuth doc, specifically the bit about scope:
http://code.google.com/apis/latitude...rest.html#auth

I've checked out your code from git and the only bit I could find that looked scope-related is this line (line 20) in googlelatitude.cpp:
GoogleOauthAdditional.insert("scope", "https://www.googleapis.com/auth/latitude");

Should this be asking for "latitude.current.best" or similar, rather than just "latitude"?

I don't have a compilation environment set up to try different settings out.

Could you have set permissions manually during development and not added code to do it in the released version? Could you revoke access in your Google account settings and then try authorising again using the released version of your app to see if it stops working?

Hope this helps. Thanks for your assistance.