Have you tried inserting your card into your PS2's other Memory Card slot? Try cleaning the contacts of the card too.
Originally Posted by fulmwaloo
If all that doesn't work, it could be that the card has become faulty...
Is your card a genuine Sony 8MB Memory Card? If it isn't, it probably isn't too surprising that it has become like that.
Unmodified SCPH-77006 with SM 3.6
SCPH-39006 with M-chip modchip, SCPH-10281 NA and refurb Seagate 80GB HDD
SCPH-10000 v1.00 with SCPH-10190 PCMCIA NA and SCPH-20400 HDD unit