You could always write a quick script that gets the current selection, does a Flatten action, then re-selects the original selection. Or was that one of the 5 workarounds?
Create a box. Convert to Editable Poly. Add an Unwrap UVW to it. Select all the faces, and use Mapping > Flatten Mapping. Smash face. The reason for the face smashing is because 2008 now DE-selects all of the faces that you just flatten mapped, whereas before, anytime you would flatten map, it would DO the flattening, but…
Err, yeh, weird... A rapid solution to the problem would be to designate an id (set id) for those particular faces, give them a texture or lastly make a selection set. That way you can always recall a selection even when max tries to fart on you this way. I would personally go with no 1, you shouldn't lose the selection if…
Hey Don, Stop by, I've got a quick UV shift script I use that will move your selected UV's in one direction or another so that you can bake out normal maps, AO maps, or in your case, quickly select flattened UV's and then re-shift you're other UV's back to the 0,1 space.
Weird that it works that way. I imagine this is in the 5 different hacks you've already been using, but: Could you move your existing cords by 1 in a direction, and then use the default unwrap area as a worksurface? Then just move everything back with -1 in the end? Irritating, but at least that way the flattened stuff is…