I've actually had 2 problems with memory when it comes to video games, the first was with a Genesis cartridge of Phantasy Star IV, which was actually my first time with the series. Both myself and my older brother tried to play the game which was pretty fun back in the day. I was into the story and still pretty new to turn-based RPGs but for some reason the game saved but the memory didn't work on the cart. After playing the first couple hours of the game several times I gave up on the game for a long while, only to figure out the pleasant rattling sound the cartridge made was the internal battery dislodged from the board! A little drilling and some minor surgery later and the game was playable again!

Second time was just after I got a Sega Saturn, of the games I had one of my favorite was Shining the Holy Ark, another amazing game I had the joy of replaying the early portion of the game several times over because I couldn't get the system's internal memory to work! For those of you that aren't in the know, the Saturn had a memory cartridge slot as well, but it also had a limited amount of internal memory, and again the problem was the battery. Now if I read the manual I'd probably have known (never do) but there was a little plastic tab like you find with a lot of battery operated gizmos that blocks the current, and I never pulled it out to keep the data saved when the console was turned off. Another great game once I was able to save my game properly.