It also does not seem to be an issue with the battery, because I restarted and my saves are working fine now too. My method of saving is as follows:
1. Play game on SRAM, save in game, power off the DS.
2. Power on, overwrite previous .sav from SRAM.
3. Power off again.
4. Next time I play the game, I always load from the .sav - even if there's still info on SRAM.
I'm pretty careful to overwrite the previous .sav after each session so I don't lose what is on my SRAM in case I should decide not to play it again for awhile. It just seems to randomly decide not to load my saves after every few sessions. Strange. Would it be more stable to use NOR instead of SRAM?