Was there a warning message when you tried to revert?
The only warning message I got was upon attempting to lauch the library. The message stated that I need to update the library, which I did. It then opened normally, but the Revert to Original field was grayed out for all pictures.
There was no warning or message when I tried to Reert to Original. Just no response.
The peculiar thing is that some of my libraries (especially the newer ones) seem to perform normally with regard to the Rert to Original command.
What version created these older Libraries?
I'm sorry, but I don't know. I have had several previous versions of iPhoto. The library most effected is from 2008. Interestingly, some photos in the library will show Revert to Original during attempts to edit them, and they will indeed Revert so long as they are not saved. Once saved, the Revert to Original greys out. In addition, some pictures will show Revert to Previous during attempts to modify them, but will not revert to original.