Before you try ACAtune at all, please make sure it's really required: If you have Kick3.1, then you won't need it for adding memory. Only if you have Kick3.0, you'll want it in the startup-sequence. Use
If you're adding it fairly early, so a shell window won't be opened which later on causes the annoying "can't change screenmode"-requester.
If you just want to check if everything is working correctly, don't add it to the startup sequence at all, but just execute it without arguments in a shell and watch the output.