PS2 gets buggy when it comes to PS1 Memory Cards.
Another little bug has been found in the PS2, but it was one known by Sony and had been addressed quite awhile ago. It seems as if PS Mem-Cards can get corrupted if they are left in the PS2 when the system turns off. This little "bug" is more or less an overlooked con that is addressed by Sony in the manual of the PS2. Roughly the manual asks the user to remove the original PS cards from the Magic-Gate before turning of the PS2. But here is a little twist, the problem was only addressed with the new batch of PS2's, the ones that were shipped with Disk 1.01. Hopefully this little problem gets fixed when the US version of the system appears.