The problem will be conducted interference. The large surge of current required by the starter motor causing the computers supply to disappear monetarily.

What fixes these problems nearly 100% of the time is to run your power (motors & weapons) on a separate battery entirtely to the control and radoi electronics. The electronics then controls the power stuff via opto-isolators. NEVER connect the two together electrically - they must be isolated.

This has been the solution to numerous people who have emailed me for help with this kind of problem. My site that gary cairns pointed to above contains information on how to achieve this, with links to sections on optoisolators.

Good luck!