Lost my iphone apps?

Ive had my new 3g iphone for a couple of months now and all was well. I pressed the home button to start up and check my mail when, i noticed about nine apps that i have bought from the apple store have gone, there are three still there. Ive connected to my ibook to try and reload them, they are there though they have been blanked out and wont open. my computer tells me that i have changed my settings, though im sure i didnt, im not very good with computer stuff and have no idea how to get them back. some of them have information on that i dont want to lose. Help !