Sony Bravia does not show! help??

hi my sony bravia 40 inch wont show anything. my sister was watching some show on kids on demand and when it ended it turn black. i changed the channel and it was still black. i pressed the guide off the tv's remote and it said video not available. i changed the channel several times. and it stayed black. i turned off the cable abd tv off and turned it on and nothin happend. i had this tv for 2 months.i unplugged the wire and plugged it back and turned it on. and itstayed black. what happend and why wont it work plz help