[ChrisH09]

Maybe HTC implemented a power save feature within Froyo to turn 4G off if there is no signal avaiable. I'm not sure what kind of signal you get where you are...but this could be a cause. If that is not the case try hard resetting your phone. There have been instances where after updating your phone to a new ROM some things doing work at first, but generally work after a hard reset. Don't know why...but if you ask anyone else this is the general consensus. It would also help to tell us where you live (town) and if you have (4G) signal were your at.