OK here is some more weirdness or clarity.
I was wondering whether there was a difference between older (2 years or so) cards and new cards.
I inserted an older card into the port on my monitor and lo and behold, it mounted. Then ejected and tried the other new cards. Nope. I then reinserted the first one and it did not mount.
Restarted the computer with the first one in the slot. It mounted. I ejected it and immediately reinserted it; it mounted again. Then I again tried the other new cards; again no go. I then. you guessed it, inserted the first one (that worked previously) and this time no go.
Repeated the restart with the old card in place; OK. The old cards worked, but the new ones didn't. Once again, the first one that worked, now won't mount.
Restarted with one of the newer cards in place. Nope.
Restarted w/o any card in slot. Inserted card A; it mounts. Inserted card B; it mounts. Inserted Cards C + D; neither mounts. Now inserted Cards A + B again; neither mounts.
So to recap . . .
Card A: 2gb SanDisk Ultra II (old) — mounts on and after start-up and re-insert but not after trying Cards C + D
Card B: 512mb Kingston (older) — mounts on and after start-up and re-insert but not after trying Cards C + D (I had forgotten about this one before.)
Card C: 4gb Lexar Platinum II (newer) — does not mount no how
Card D: 16gb Lexar Platinum II (newest) — does not mount no how
There seems to be a pattern here. Maybe there are card differences.
Chris