Owners of T-Mobile G1 phones with Google should have received an over the the air update (RC29) to their phones either in text message or automatically. The new version has the browser patch that was missing in RC28.
Developers in the Android community are saying that you can upgrade through downloading a file, unzipping it and loading it on to a microSD. They warn that data can be lost in the process.
Comments suggest that is better to wait for the update to be delivered to your G1 Google phone.
T-Mobile says that they understand that many have downloaded this update and
seem to have it working, T-Mobile cannot support you in doing so. If
you download and attempt to install this or any other update
(regardless whether its from Google or not) to your device, and it is
rendered unusable, you are out of luck. Even if we do exchange it, you
will be without a device for several days.
Wireless and Mobile News agrees that it is better to wait for the upgrade to avoid voiding any warranties. We still haven’t figured out why selling the phone at Wal-Mart is considered a controversy for the G1 phone that reviewers rated 3.5 out 5.