You can boot your T-Mobile G1 Google phone into Safe Mode if you wish to troubleshoot whether or not added applications are causing problems with the device. This mode will only load basic software.
1. Power the device off.
2. Power the device on.
3. Right after the G1 screen appears, press and hold the Menu button. Keep holding it until you are booted up completely. Safe Mode should appear in the lower-left corner.