The Action Replay for the Game Boy Advance is a cheat utility that connects into the Game Boy as a game cartridge. Once connected, it boots up into its own settings menu and allows you to configure cheats and modify runtime memory for Game Boy games. If the Action Replay has undergone settings changes that cause an error in its boot sequence, it will display a fuzzy white screen and will not begin loading. You can fix this by performing a factory reset on the Action Replay's configuration.
Insert the Action Replay cartridge into the Game Boy Advance.
Turn on the Game Boy Advance while holding the "A" and "B" keys.
Press the "Start" and "Select" keys as soon as the Nintendo logo appears. Do not release "A" and "B."
Hold these keys down until the Action Replay begins to initialise. It will detect the key sequence and immediately reset to its factory default state.
If resetting the device does not work, contact the Action Replay customer support team. (See Resources).