Okay, here's where we are...
I followed the instructions on this page, specifically the section entitled: SD Card >4GBhttp://chdk.wikia.com/wiki/FAQ/Mac
I was able to partition the card into a small partition of 9megs of so, FAT16, and a large partition of the rest, FAT32
I edited Bootsector.bin with 0xED, and loaded it back on the SD card.
I then copied the DISKBOOT.BIN and the PS.FIR files to the small partition, as directed.
I then copied the CHDK folder and the vers.req file to the large partition.
I ejected the card, locked it, inserted it in my camera, and had the same problem - it worked, it loaded CHDK, but it told me I only had 8 megs available in memory (the same size as the first partition).
Now, the very interesting part, I think. When I load the card back into my reader, and use my Mac to look at what files are in the partitions - lo and behold, there is now a CHDK folder in the FIRST smaller partition. I didn't put it there. I even deleted it, loaded the card back in my camera, CHDK launched, and it put the folder back in the first small partition.
Is that why it thinks I only have 8 megs of memory - because for some reason it's loading CHDK in the first small partition?
And if so, why, and what do I do about it?
Thanks guys for helping on this.