I'd recommend posting at http://forums.adobe.com/community/lightroom?view=discussions
as that gets a wide coverage by Adobe staffers.
However, are your images on an internal or external drive? In other words, could the drive letter have changed? Or could the files have been moved? That would also be indicated by a ? by the images in grid view or by the folders in the folder list (if whole folders have gone missing). If the image files are not where LR thinks they should be, you'll still see the images in Library (grid or loupe) as it uses previously-cached previews, but develop module needs the images online.