Comes up asking to reboot the htc

Could be that your update failed and your phone is now soft-bricked. Take it back to your carrier's service center and they should be able to fix it. Or if it's out of warranty, find an expert near you.

What happened before the white screen problem?

Hi
Try hard resetting the phone.Here's a video tutorial on how to go about it.





Hope it helps.

hi free_b_73 this sounds like your phone is doing a hard reset on it. Right now phone is doing what is call a hard reset. The our problem is that the phone has not finish yet. GO to hboot and see if that finishes. the phone should go come on all the way now. Next your going to have to reactivate the phone Set the phone up again. after you get the sim going I would get your gmail back on the phone this should reinstall your contacts and apps on the phone. this should help let me know if this works.

I’m happy to help further over the phone at https://www.6ya.com/expert/ronald_e152e07e272e4f27

please take the battery out and then follow the below procedure .
Click here

release bacover and press reset button,if the problem still continue.,Hard reset is the best way to solve/turn off>press and hold volume up and down,including power button. note:hard reset will delete all ur data and turn ur device into defualt....

this happens when you have one side button jammed, look for the jammed button and press it many time to relese it,
regards
please comment

Hi there,

Looks like you should try to Hard Reset it.

This is done by having your HTC Diamond turned off first.

Then, hold the VOLUME UP and DOWN buttons at the same time and briefly press the POWER BUTTON.

Now keep holding down the VOLUME UP and DOWN buttons until you see a screen

At soon as you see this screen, you should release the VOLUME UP and DOWN buttons.
Now press the VOLUME UP button to complete the hard reset. Now this will completely format your HTC Touch Diamond as if it was turned on for the first time from the box. Everything once previously on the phone will be deleted including messages, contacts, music and the like. Hope I have been of assistance to you, Cheers :)

format or flash your phone using data cable

the HTC needs to be reflash to correct this issue...so take the phone to a mobile service center to have that done or try sourcing it online.