Sounds like an acpi bug in the bios, or kernel toward your bios - see if there's an update for it. Anytime I've had suspend issues, it's almost always a bios thing, particularly in Dell, or or kernel folks begrudgingly write an exception to deal with popular, crappy hardware.
This issue single-handed holds back linux in general on laptop hardware as every laptop is different, where the vendors usually write crappy windoze code and drivers to work around their poor, non-standard bios'.
If you're using grub/legacy bios, might try EFI if it supports it. Not sure how much will follow through and plague you, but might prove better, or at least more standard these days. Dell is at least one that actually *does* consider linux vs. the lenovo, toshiba, and hp's that still pretend no one uses linux desktops.