"P. Dwayne Miller" <dmiller(at)espgroup(dot)net> writes:
> It appears, and I could easily be mistaken, that the COPY command does
> not allow NULLs into a timestamp field, even though the field is defined
> to accept nulls.
Not sure what your problem is, but that's not it. Perhaps you've got a
problem with stray carriage returns (\r\n instead of \n), or what you
have in the file isn't actually equal to what you specified as the WITH
NULL string, or something else.
regards, tom lane