I have sent email to support at HTC with same problem and oddly enough, same processor and graphics card.
Here is the reply I received:
"There are a number of things which could cause this. Heat, power, drivers
(Vista drivers are not as robust as they should be), background processes
wanting resources the game needs (iTunes, Quicktime, any Adobe or Intuit
product, as well as anti-virus software *Norton being the worst)."
Hope this helps,
TimRN