In 2.6.18, you have to change the disk mode from AHCI to compatibility mode in the BIOS to make disk work after resume from suspend to ram.
After applying the following patch from Forrest Zhao http://lkml.org/lkml/2006/7/20/56 both suspend to disk and suspend to ram work fine now in 2.6.18-rc6 with disk in AHCI mode (default). Huge thanks to Thomas Glanzman for help in tracking this down. This patch won't be in 2.6.18, but might make it in 2.6.19.
Older kernels don't work even in compatibility mode, you need this patch: http://vizzzion.org/stuff/thinkpad-t60/libata-acpi.diff