Was it a photo that you synced from one of your pic folders on your PC? If it is, prior to the iOS5, I realized that I could not delete pictures that were synced from itunes to my ipad. I have not confirmed this with the new OS, since I unmarked all pics going onto my pad prior to the big update to save time in backup. I actually had to unmark the folder for the next sync to remove that picture. If it is a picture you have taken on your ipad or downloaded it from a website/email-you have that choice of tapping and deleting it. You will see a trash can icon in the upper right hand corner. Hope that helps you!