I could only recommend trying the downgrade, but this will be useless if Pleo does not register a memory card, it can't hurt of course. You can find it under the software thread, try the proper downgrade first, if that fails then try the POP (point of purchase, demo mode) hopefully they will help, as I said they cannot do any harm since your Pleo is already non operational.
Also make sure you have the drivers for Pleo installed, if you are running windows 7 try running the driver in vista compatibility mode, and make sure Pleo is turned on.
If that fails definitely contact pleoworld, even if your Pleo is out of warranty.