Android Google Talk Broken Changing Googlemail To GMail
Changing your Google login from @googlemail to @gmail will BREAK your Android Google Talk app.
Has your Google Talk app stopped working since you changed your Google account login from ...@googlemail.com to ...@gmail.com? There is a known issue with this. There may also be problems accessing the Android Market.
Due to some boring legal reasons, Google had to use the name Googlemail in the UK as opposed to GMail elsewhere in the world. Recently, they have acquired full use of the GMail name in the UK too and when you login to your Google account on your PC you are given the option to change your login from Googlemail to GMail. No problem there, as the email logins and addresses are used interchangeably. But the Android Google Talk chat app on your phone will stop working and repeatedly display login failures. Currently, Google's suggestion is to factory reset your phone and then use the @gmail login when you set it up again! Err, no. Hardly ideal. Google are working on a fix for it. It's no good fiddling about trying to change passwords and change them back either, the username is fixed and that is what's causing the problem.
For now, you will have to revert back to your old googlemail address. Do this by going into Account Settings on your PC and clicking Switch to @googlemail.com.