Hi nak50 and thank you!
The error you're getting indicates something's wrong with your sfall installation.
How did you install the game? Did you install any mods or copied over the game files into an existing Fallout 2 installation?
In any case you can fix this by opening ddraw.ini, finding this setting and changing it to this
Code:EncounterTableSize=49
Went into ddraw.ini & found the setting, but it was already in there as you'd written. Another idea?