The GameCube is picky about its memory cards. Official Nintendo cards (gray, black, or white) use "MagicGate" encryption. Many third-party cards (Mad Catz, generic brands) do not.
Early GameCube copies of Resident Evil 4 were prone to data corruption, often triggered by third-party memory cards, requiring later "Player's Choice" versions to resolve the issue. Modern solutions involve using specific "GCI" save formats in the Dolphin Emulator or using community-driven HD project patches for PC versions. Detailed discussions on troubleshooting these save issues can be found in the GameFAQs forums .
This write-up outlines the and a step-by-step fix for recovering or restoring a functional save.