Help Can't ugrade my phone firmware


i downloaded kies yesterday and it said that there was an upgrade for my cellphone, so i decided to intall it, but when it gets on 80% it comes back to 0% and says that there is an error, and it stops the upgrade, i dont know why, i have done it like 5 times and its allways de same, someone can help me?

my os is Froyo 2.2