Check and make sure you have all 3 legs of power comming in.  If it get stuck in the boot up stage and does not go any further, it's possible that you lost a power leg.  If that is not the problem, a cold start might be needed to clear the problem up.  Is this an S4 M94, S4C M98, or S4C+ controller, because they are all different in how they cold boot.  Cold boothing consist of shutting down power and pulling the battery back up to clear the system.  Then you load the boot disk starting with the system key then disk 1-4 or 1-8 ,as the control ask for them.  Loading the parameters and actual program from your disk might take a few attempts as well.

Send me an email and we can go into this much further.   mdgwelding@yahoo.com