I moved the folders but ended up accidentally deleting them all. I freaked out but was fortunate enough to find a free restoration program that recovered all my pics. Phew!
I think the problem is the limitations Windows 7 places when you add or remove folders within Libraries. If one doesn't "register" the folders in the correct manner, certain folders will end up "locked". That's the only explanation I can come up with. For now, I'm going to "properly" include these pic folders within the Pictures library in the way Microsoft wants and see how that goes. I can open the folder I couldn't with no problems.
Anyway, thanks for all your help Latios.