Re: Removing Flash Glare?
In my experience if you try to remove flash reflections from glass etc. with curves or whatever, things start to look retouched very quickly.
The only option I see is: Get rid of the picture altogether and replace it with wallpaper, another picture, .... If you're client pays well and is not too far away, go there again, shoot without flash (but perhaps with a tripod :-) and replace the picture with the new one.
If you're lucky and the picture has the flash spot in different locations on different photos, copy/paste with heavy feathering from one photo to another. Subtle changes in perspective will most likely be less obvious than a bright spot - usually you get away with something like this in the background as everybody looks only at the faces anyway.