Application update problem iPhone

HELP!! I had to clear everything from my phone when I thought it was lost. Then I restored it from my backup on itunes. Now when I try to update ANY of my apps I get the message: This discounted price is only available to customers who own a previous version of this item. To purchase this item at full price click buy.
Its as if I dont have the apps on my phone at all but they do all work fine. Cant go any further bec. of this.
Then in itunes I looked for the updates and it shows that I have some but when I click on the arrow to get the updates it goes to the next page and says that all apps are up to date. Very weird. Hope someone can help bec. I cant find a thing about it!! :((
Thank you!
iphone 3G iPhone OS 3.1