Iphone 4 non responsive

my iphone 4 was fully charged when I went to bed last night. It is my alarm in the morning for work. When I woke in the morning it was not responsive- it was just a black screen.. I plugged it into the wall charger and i received a bit of life, but it just told me to connect to itunes. I restarted it a couple times (held the top button and the home button down at the same time but it still didnt worrk. The phone told me to connect to itunes. Once connected to my compuer itunesndownloaded an update and tried to ( unsuccessfully) install it on the iphone. It haltd a few seconds into it and gave me an error code 2009. What does this mean. Hkw do I get my iphone to work. I did nothing out of the ordinary from my dag to day activities with the phone. It did not drop or touch water. Why did it fail? Please help I dont want to buy a new phone.