Edit: Just noticed that the acer_wmi module doesn't really have much to do with your suspend problem - more than it's blocking suspend. If you find the module responsible for blocking suspend, just switch out its name with acer_wmi in the following suggestions, but without finding the responsible module, my suggestions probably aren't going to help you too much.
The traditional way of troubleshooting suspend where there's a known driver issue is to force the unloading of that module before suspend. You'd do that by running
sudoedit /etc/default/acpi-support
And looking for the MODULES="" line and changing it to (in your case):
MODULES="acer_wmi"
But reading the comments at the top of /etc/default/acpi-support, I'm not sure that's still going to work. Give it a go.
If it doesn't, you might find a short script like this fixes things:
#!/bin/sh
rmmod acer_wmi
pm-hibernate
modprobe acer_wmi
That will need to be run as root, so whereever you save it, you'll want to run it like: sudo bash ~/my-suspend-script.
I feel like there should be a good way to hack this into the /etc/pm/sleep.d/ system but I don't know enough about it to say conclusively. Perhaps something like this:
#! /bin/sh
case $1 in
suspend|suspend_hybrid|hibernate)
rmmod acer_wmi
;;
resume|thaw)
modprobe acer_wmi
;;
esac
That would be cleanest in terms of integration if editing acpi-support doesn't work.