i woke up this morning and had another look and realised straight away that the problem was with the bitmap.
that had got corrupted during the crash and of course litestep would have problems trying to load a corrupted bmp.
looking at it with a fresh pair of eyes helped (as usual)

it is curious though cos, as you say warma, i dont know what could have happened to corrupt the bmp.
i cant remember exactly what i was doing at the precise moment litestep crashed but i use paintshop and that normally works perfetly well without either litestep or windows explorer.

i guess it was just some random one in a million thing