1. put the screws back that you already removed and tighten them back up this might remove some of the stress.
2. try the awkward screws again
3. slacken all 4 equally, the same way you would when tightening them.
edit....you could also try tightening the awkward ones as this will crack any adhesive that may have been used.
Tried that, no luck.
you need to use a rubber band like this:
Funnily enough I don't even have a god damn rubber band. You'd think there'd be one lying around.