Thanks Nick, I will drop a report of there. In the mean time others giving V1.5 a fly are warned!
@RetroleftyClearly IDE 1.5 is a beta release to let people play with their new Due boards and is not suppose to be a replacement for the current production 1.0.3 release for all the other arduino boards.
It is clear that it supports Due! However, it is not clear, that it is not supposed to be a replacement for the whole range of Arduino boards! The developers have not made it clear & I gather neither of us can read their minds.