did you try to reboot the phone or pull the battery?
let's back it up a second--
how are you attempting to access the front facing camera?
through an app?
through settings?
through camera setting? (camera--depress ">" icon on screen--depress bottom WHEELS/COGS icon--top setting "switch camera")
might have to go and become friends with a SprintTechstill under that 1yr HTC warranty--so you're covered for a replacement!