lucy24 - 8:22 pm on Jun 8, 2013 (gmt 0)
And forget the detection coding which normally works fine to redirect mobile users to our mobile site. Google stops that function from working at all.
Out-on-a-limb possibility: google is setting a cookie under your site's name that overrides your user-agent detection. This is conceptually possible, but would only work if (a) g knows the cookie exists and (b) the visitor accepts third-party cookies. And even then, it can't make your site do something the site is not already programmed to do.
Study the server logs and possibly also the request headers to see what's happening behind the scenes.