Reverting Iphoto to previous version..

I accidentally upgraded my iphoto'08 to iphoto'09 during remote access. My Imac has iphoto'08 and my macbook has iphoto'09. I remotely accessed my Imac photo libary in my macbook, now i cannot open my photo library in my Imac, it says "*You have made changes to your photo library using a newer version of iPhoto. Please quit and use the latest version of iPhoto"*...How can i revert the new changes please help, i cannot find any topic for this...
Help...