Renault Kangoo immobiliser scary stuff!?

Can anyone help i have a scary van!!
Had problems with immobiliser, had the fuse box checked terminals cleaned etc OK for a couple of years. Now the problem is, while driving along it can just cut out without notice even at a steady speed. thankfully i wasn't on the motorway. Same lights come on as before and restarts are varied from straight away to fiddling with the muilty fuses. Could this problem be connected with the immobiliser?

Jim
June 2009