I've played Aftershock for a while, about month or two ago. I didn't have enough time so I uninstalled it. Now I wanted to try it again. And to my surprise, Aftershock crashes on startup, with nvopenal.dll error. The PC and system is exactly the same, nothing changed. It is quite old, Athlon 1,3 GHz, 1 GB RAM, GForce 5900, winxp with sp3, but not TOO old for Aftershock. Between first and second Aftershock run I wasn't making any changes in the system. No new antivir or firewall (I have KAspersky and Sygate PF). Maybe only some windows updates.
I've tried to download and install Aftershock again, using GOG Downloader this time - no change.
Nvopenal.dll is version 5.10.2917.0, try to find a newer or older? Any ideas?

Try reinstalling your graphics drivers.
Maybe getting a newer version or rolling back to some older would help too.