I was having this issue while deployed and it was driving me nuts. Basically, Safe Sleep is a pain in the butt and causes this problem in the newer Macs. Also, there's more on Apple's Discussion Forums. A widget is available (called Deep Sleep) that will allow one to avoid using the Terminal. Also, more info about disabling Safe Sleep here on macosxhints.com; Apple really needs to rethink this one.
So, To Disable Safe Sleep:
Type these two commands in the Terminal, and hit return:
sudo pmset -a hibernatemode 0
sudo nvram "use-nvramrc?"=false
Presto, instant fast sleep, and no more crashing!!
Now if you want to reclaim some hard drive space, an amount of space equal to the amount of RAM your computer has, do the following:
In the Finder, choose Go To Folder... from the Go menu
Type "/var/vm" into the prompt and hit return
Don't touch the swapfiles, they are important. But if there is a file in that folder called 'sleepimage', just drag it to the trash and you're good to go.