Ive seen this problem many times with the 580i, Although the screen doesnt look damaged, it actually is. You'll require a new screen which costs around £20 , if your case is damaged aswell a full replacement case will cost around £13 which comes with a complete sony ericsson branded case with new buttons included as these break easily aswell. Your files and contacts are generally safe on your mobile and usually arnt lost during repair.
If you would like this repair to be done to your phone professionally for you, I can do this for a fixed fee of £5 + the cost of the parts required.
If you would like further information, please contact myself at drewishuk@yahoo.com
Thanks
Andy
Andy, May 2008