ok sorry to get confusing here, but i am back on track now.
seems avisynth was playing a roll in this problem. i uninstalled avisynth, reinstalled it, loaded problem m2ts and i now get no issue with error700
but it crashed as soon as i tried to index
turns out to be if there is a DTS track this is causing the crash, as if i choose set no audio track, then it indexes fine
all is working fine now as long as i set no audio, would it be possible to have a drop down option to tick off audio demuxing?