This issue seems to be resolved. Here are the notes that I wrote up in our internal system regarding this incident:
User reported the server went down last night due to a power outage. After rebooting the server, the AFP/SFM shared volumes were not accessible to the Macs, but the SMB volumes (even the same folders) were accessible to both PCs and Macs. The server did not show any error messages in the logs regarding this issue. I was not able to find any configuration settings that were not correct (none had been changed), but the AFP/SFM volumes starting coming back on their own one at a time, with the Production volume (320GB) coming back after five hours from the boot time. It would seem the server needed to recreate a AFP/SFM index, but I do not know which one, how to monitor its progress, or how to initiate it should it fail to come back the next time.
It looks like I got lucky and the server fixed itself. Thanks for your help though.