Have you tried resetting them?
They big question is if it's a hardware or software problem. When you say "stopped being able to read any programs on Micro SD cards", do you mean skits? Have you tried programs that don't rely on the active OS running (such as
StatsRB) or just writing a simple startup script to see if the low-level OS is still reading the card).
Then there's the cards . . . are other pleo RB's able to read those specific cards? Or have yoy tried cards that work in other RB to confirm it's not a bad/unreadable card?
If it's truly hardware, you stuck with a cute toy. If it's a software issue, there are things to try, including a basic reset, or reloading the OS.