1) When Dr. Brooks took the photo there was sunlight coming in through the windows behind Hurley. But when Brooks shows Hurley the photo the windows are pitch black.
2) Two people sit by the left side of the table behind Hurley when the photo is taken and should be visible in the photo, considering the angle at which it was taken (the angle seen in the photo later). But in the photo only one (the one on the right) appears (barely visible, behind Hurley). Was the guy on the left imaginary too?
3) In Libby's flashback Hurley turns his head towards invisible Dave after the flash hits, while in Hurley's flashback, he turns his head just before the flash kicks in (he turns it back just in time to look at the camera when the photo gets snapped).