Full Memory Card
Playstation One memory cards accumulate a certain amount of data before running out of space. If the gaming console is unable to read the card, it could be full. To check if the memory card is full, remove discs from the console and insert the memory card; this brings up the game's menu. From there, choosing "Memory Card" and pressing the "X" button brings up the Memory Card menu. Blocks of data are displayed on the screen. If every block is full, it means the memory card is full. Highlighting a file and pressing "Delete" frees up memory space.
Unlicensed Memory Card
There are a variety of memory cards produced by several third-party companies. Many of them are unlicensed and work for a period of time before failing. Sony says it can't guarantee that unlicensed cards will work. In fact, the company recommends only using memory cards with the official Playstation logo on the card. An official PS1 memory card is "model# SCPH-1020." If you're using a card that isn't produced by Sony, it is likely running into compatibility problems and should be replaced.
Damaged Card
If the memory card you're using is damaged, the Playstation One freezes or run into errors when you try to save and write data. Exposure to extreme temperature and water damages memory cards. Improper use and storage also cause dirt to accumulate on the metal contacts. Inspect the contacts on the memory card. If they are dusty, cleaning them with a soft, dry lint-free cloth improves the reading process. Abrasive solutions, such as glass cleaners, damage the contacts.
Tips
If possible, testing the memory card with a different PS1 console tells you whether the card is the problem. If the card does not work with another system, replace it. If it does work, the gaming console is probably faulty. Unfortunately, Sony says it's no longer servicing Playstation One gaming consoles because they are older systems. The company recommends upgrading to a newer gaming system.