Errors in writing output file using ifort

I am converting some code from NAG to ifort 9.0. I am reading a 9022x3086 1 byte data array and i am using -assume byterecl and increasing my ulimit to do this and it all works fine. I then do some processing on the array that turns it into a 2byte int data array. I then open a file sequentially to write a header and then the data array.



OPEN(unit=nimrod_store(id)%ref, file=TRIM(nimrod_store(id)%name), &

status="replace", action="write", &

access="sequential", form="unformatted")

!

! Write the header data