thank you very much for your reply.
the way i created the disc originally was like your number 2 - i imported the clips as assets and added them to a single timeline. this previewed as i expected (all the chapters worked) but when i created the bluray folder and tested with arcsoft there was 21 titles each with 1 chapter (not 1 title with 21 chapters)
i hadn't heard of problems with Arcsoft (i didn't look)
i will try a previous version or install PowerDVD.
if i still have problems i will try your other suggestions