I had this problem using etch on a Thinkpad X40 with Intel 855, which had previously worked fine under sarge. Switching consoles didn't solve it; X needed to be restarted. However, using s2ram (NB not s2disk!) from the uswsusp package rather than echo mem > /sys/power/state has restored it to working order. I don't see why, but it may work for someone else.