I have had similar problems myself with igniting MH lamps at some distance from the control gear.
A quick fix that works with inductor/choke ballasts (230V system) is to swap the MH igniter for a HPS igniter, preferably of the long-range type. This will not harm the lamp or control gear, but it does produce a much more energetic ignition pulse which will ignite the lamp despite the cable length. Do use an igniter for a lamp of the same wattage, ie a 400W HPS igniter for a 400W MH.
Alas, I cannot confirm if the same trick will work with 115V ballasts.
Mark M
