I know Sprint in the USA honors HTC's Warranty which saves the time of shipping and receiving a Diamond from HTC.
Speak with your Carrier and see if they have the same policy. If not, try to encourage them to help You.
If the above fails, contact HTC and they will give you an RA# and will repair or exchange the Diamond for you.
It goes without saying to call HTC first and explain the issue to them. I wouldn't tell them that you Flashed a ROM as you don't want to give them an excuse to not replace/repair your Diamond.
Good Luck
and keep me informed.
If I can be of further service, don't hesitate to ask, and I will help you out if I can