I recall having two memory glitches or other problems (not counting how Okami on PS2 occasionally corrupts my third-party PS2 memory card, making it impossible for any other game to save to it... and you can't delete the saves unless you reformatted the card somehow. On that note, I hate when you're not allowed to move (and/or delete) a save game file. Looking at F-Zero GX and Smash Bros. Brawl here).
I got every character and course in Mario Golf, including the last secret character (thanks Dan from the Donkey Kong 64 / Jet Force Gemini videotape with the over-hyper Steve). But then as I was going through the menus one time, everything froze. I reset the game to find ALL my saved data lost. I didn't have it in me to unlock everything again.
And my Donkey Kong Land cartridge is unplayable, the graphics are all glitched up. It was hard seeing things in that game due to all the detail thrown in (I think you needed a Super Game Boy to have enough colors to tell what was going on), which is why glitched-up graphics made it that much harder.
I suppose it doesn't bother me that much in the long run since it rarely happens, although I'm sure there are some people who face this problem more often. I can't think of any alternatives, any way to mitigate this problem other than copying the save data to multiple memory cards or backing up to computer somehow or keeping the cartridges in a nice cool place. I guess just treasure your saves while you have them.
A few vaguely-related incidents:
- Rented Sonic the Hedgehog DX, it immediately popped up an error that the disc was unreadable due to dust or whatever.
- Rented Burnout 3 for PS2, it couldn't get past the menu loading screen.
- In Star Fox Adventures, I faced the glitch in Cloudrunner Fortress where you return the children to the Queen Cloudrunner... then you fall through the floor into a pink void. My solution was to leave the fortress (easier said than done) and come back.