I can't remember.

Something like that happened to me... but for the life of me I can't remember what it was.

If I had to hazard a guess I'd say it had to be either Final Fantasy or Legend of Zelda. (The OGS)

because of it... I compulsively save.

Like if see a save point in a game with save points, sometimes i'll save 3 times in a row for no damn reason.

It's really a bad habit.

That reminds me of another one, where I screwed myself over in BioWare's first Neverwinter Nights with a bad save, so I started having duplicate save files in any situation where I felt a single save could leave me in a situation I can't get out of.

Though looking back, I was a total RPG noob when I played NWN, and I probably could've just gone elsewhere and grinded til I could beat the boss I was at, but for some reason at the time I assumed the game rules wouldn't let me do something like that.

My brothers deleted my Gran Turismo 1 file. They thought that they could delete a single block from my save file in the memory card....

Extra: The worst game file loss I've caused.

A friend lend me his Dreamcast for a few days. There was a power outage when Soul Calibur was autosaving (he had it on and I didn't touch the options) and the data was corrupted. I spend an entire day unlocking everything again, but the records were lost.

Hah, that reminds me of FF2.   I went through the whole game way underleveled using tactics and items... then couldn't beat the final boss... and was stuck in the final dudngeon in a savepoint right before the boss.  Just quit because after looking what level your SUPPOSED to be in the strategy guide, I realized it'd take me forever to get there care I was like 10 levels below the minimum.

I think it happened only once.
I lent Starfox 64 to my friend`s cousin and when he returned the game all my sweat earned medals were gone. I didn`t have them all but i was close. And i had worked so hard to get them.
He`s excuse was, i think, that he wanted to play from scratch.

Lesson learnt: don`t lend game to others or they will erase your starfox 64 medals!

ouch!! same happend to me with ff7, was at disc 3. i saved over my own file by accident. Had to start all over again