http://mytreo.net/forum?topic=9927.msg98507 discusses a double-reset procedure as a workaround for When Installs Go Bad. Be interested in hearing from others who might have tried this.

1. Hold the up button while you treo is resetting;
2. When the grey 'palm' logo screen shows up you manually reset your device (hole next to battery) and release the up button;
3. You now get the time pref screen which you can disregard;
4. Now select your phone application through the phone button;
5. Add 'Filez' and/or 'Destaller' (if you haven't already done so) to the favorites page and start one of them;
6. Now you can remove the guilty application and your device is healthy again...