Ah, my fault. The zip was being unpacked with MacZip, rather than Stuffit Expander. With Stuffit it retains the file type and it runs like the old 1.65 Update utility... however, I can't seem to get it to update.

My card is in the further slot away, labelled as Slot C on the motherboard.

I've tried entering the following:

$0C = "No Silicon Express IV card were updated"

0C = "Application 'unknown' unexpectedly quit due to error -1"

C = "Application 'unknown' unexpectedly quit due to error -1"