Thank you for contacting our Customer Support Center. We are dedicated to providing you with the best quality service and answering all of your questions and concerns.
To clarify your issue, you stated that: You are facing problem with HTC Desire S on standby mode.
In this regard we would like to intimate you that please perform restore factory settings and share feedback with us. To perform the restore factory setting you need to perform the following settings:
1. Remove the battery, wait for a few seconds, and then reinsert the battery.
2. Press and hold the VOLUME DOWN button, and then briefly press the POWER button.
3. Wait for the screen with the three Android images to appear, and then release the VOLUME DOWN button.
4. Press VOLUME DOWN to select FACTORY RESET, and then press the POWER button.
Note: - In the restore factory settings all your data will be lost. So before performing the hard reset please take the backup of your device.
This is the reply i got from HTC about my problem