Iphone passcode not working after downloaded updated 5.0 version

My problem is that I can't use my phone because my normal passcode continously is being rejected. I noticed a few days ago that I could not use the Face Time feature. So yesterday morning I downloaded updated 5.0 version onto my iPhone 4.I left it alone because it was taking so long to download. I didn't come back until the afternoon to check my phone. I discounted the phone before I checked if there were any instructions I needed to do. So maybe that's the problem! Now I can't get inot my phone because my passcode is being rejected each time I put it in. What is the problem and how can I restore my passcode with out deleting all of my other data; such as NOTES, my calendar entries etc.? PLEASE HELP ME!!!!