For anyone who has been running into the same brick wall as me when trying to import .GCI save files for GameCube games, here's what I did that finally worked after Google turned up absolutely nothing:
1. Start the game you're trying to import a save file for.
2. Once the game creates a save file, close the game.
3. In Dolphin, go to Tools>Memory Card Manager and select the Memory Card your game created a save file on.
4. Delete the save file that the game created.
5. Click Import
6. Select the save file you want to replace it with.
7. Enjoy
I've learned that two conditions must be met in order to import a save file for a GameCube game (and I would assume a Wii game as well). First, you must have run the game before. I've read posts on this forum that importing save files for games that haven't even been run yet will crash Dolphin which is no good. Secondly, you can only have one save file per game, so if you try to import a save file for a game which already has an existing save file on the Memory Card, it will fail to import.
Hope this helps anyone who keeps getting the same "Failed to import .GCI" message that I was. I scoured Google for at least half an hour and turned up exactly ZERO results.
1. Start the game you're trying to import a save file for.
2. Once the game creates a save file, close the game.
3. In Dolphin, go to Tools>Memory Card Manager and select the Memory Card your game created a save file on.
4. Delete the save file that the game created.
5. Click Import
6. Select the save file you want to replace it with.
7. Enjoy

I've learned that two conditions must be met in order to import a save file for a GameCube game (and I would assume a Wii game as well). First, you must have run the game before. I've read posts on this forum that importing save files for games that haven't even been run yet will crash Dolphin which is no good. Secondly, you can only have one save file per game, so if you try to import a save file for a game which already has an existing save file on the Memory Card, it will fail to import.
Hope this helps anyone who keeps getting the same "Failed to import .GCI" message that I was. I scoured Google for at least half an hour and turned up exactly ZERO results.