I have an Intel 320 Series SSD. When I use the full disk encryption support by setting an ATA password, I can't resume from sleep (my machine locks up). I checked to ensure my BIOS is set to use S3 sleep mode and I also tweaked Windows 7 so DIPM is enabled. When I disable ATA password, everything works fine.
I suspect the SSD is getting powered off while in sleep mode which puts it back into a 'locked' state without any way of unlocking it before Windows tries to wake up.
I'm having trouble with my desktop machine, which doesn't support ATA password in the BIOS. I have a minimal linux install on my 2nd hard disk, boot into linux, unlock my disk and (soft) reboot. That keeps the drive unlocked and everything works (except resume from sleep). I also have an Intel 320 Series in my laptop which has no problem resuming from sleep with ATA password being used.