Don't let apmd and acpid run at the same time unless you REALLY know what you're doing. Debian will not make sure only one is running at a time. You will have to check. APM will try to put your system into S3. On the 2.4.x (and before) series kernels this will quite probably hang your machine. S3 is not supported until 2.5.x. Even the patch won't provide support for S3. I personally did an apt-get remove apmd to solve the hanging problem.
You should also be aware of another little glitch I discovered. The XFree86 server has an option for DPMS (Energy Star) features. The DPMS can states can be one of standby, suspend, off or on. Since the 2.4.x kernels cannot suspend to disk, this can cause problems. I fixed my system by doing two things:
xset -dpms (disables DPMS features)
In /etc/X11/XF86Config-4 I commented out the line Option "DPMS" under Section "Monitor".