Ok, so I'm running Lion and my problem is this: I have two partitions, one Macintosh HD and one for Bootcamp. I shrunk the size of my Mac partition from 900 GB to 800 GB, thinking that it would increase the size of my Bootcamp partition to 200 GB. Needless to say it did not, but now I have 100 GB of empty "grey" space underneath my Mac partition. I want to resize the Mac partition back to its previous size, so I drag the resize slider down to fill the empty space and click "apply". It immediately reverts back to the previous description (800 GB of Mac with 100 GB of grey space) while saying "partition complete." I'm no longer worried about resizing the Bootcamp partition; I just need to get my Mac partition back to its previous (post-Bootcamp) size.