In my Emerald, everything worked fine at first, saving, loading, everything. I made it to Dewford town, then thought it would be fun to connect with XD for the battle mode. I tried connecting, and it said the game was not saved right and it was deleted. Sure enough, when I unplugged it and turned it back on, my save file was gone. Now, every time I turn off the game, my save game is gone. As a test, I tried saving in the Moving Truck, I turned it off, turned it on, and I could load the file. Then I went in the house, set the clock, and saved. When I turned it on, my save file was gone again.
Is this a problem with my battery? Is there a way to fix it? Can I replace the battery? Is there anyway to play without setting the clock first?
And, if I fix the game, and try to connect to XD again, will it happen again?
Yes, it sounds like a battery. Yes you can replace it. Connecting with XD was just a coincidence.