UPDATE:
I read this on another forum and it worked for me.
I was using the advanced task killer (never running in memory but installed) so I uninstalled it, then did a soft reset (pulled the battery) and it fixed the problem.
Here is the text from the original post I found.....
I e-mailed HTC about this and actually received a decent reply. I'm posting the relevant section:
If you have any type of third party Task Killer app installed on the device, please remove it and perform a soft reset of your device as apps of this nature can have an adverse effect on the Android OS. If the issue still persists, please proceed with the Safe Mode/Reset steps.
Please place your device in Safe Mode for a 24 hour period as it will disable any non-essential software installed on the device. If the issue still persists in Safe Mode then please proceed with the reset steps. If this is not apparent in Safe Mode, then please start uninstalling third party apps until the conflict app is found.
Enter Safe Mode:
1. With the device turned off Slide out the Keyboard
2. Turn the device on
3. Press and hold the “S”
4. You will feel a vibration and when the device loads will see safe mode bottom left
Exit Safe Mode:
1. Restart device
Reset Information -
Pulling the battery out is generally referred to as a 'soft reset'. Please turn phone off, remove/replace battery and then turn phone back on. If this does not correct the issue, then please ensure that your personal information such as contacts and photos have been backed up in preparation for a factory reset. Resetting the phone deletes all data, including downloaded applications, and resets the phone back to its initial state — the state before you turned on the phone for the first time.
To reset the device using the menu:
1. Settings > SD & Phone Storage > Factory Data Reset
To reset the device using the device keys:
1. With the device turned off, press and hold the volume down button (located at the right panel of the device), and then press the power button.
2. When the device’s display turns on, release the volume down button.
3. Use the volume buttons to select CLEAR STORAGE, and then press the power button. (All data will be deleted from the device).
** For me, the 24-hour Safe Mode approach seemed to work. Since I tried this, I haven't had a single "HTC reload" (of course, I now have other issues, but that's another thread...).
