Import Data replaces NULL with 0
Choose to save the package instead of running it right away.
Then edit the dtsx file and on your copy task check "keep nulls".
Then run the dtsx.
I didn't test it but think it will solve your case.




Testing the suggestion on the comment on express with advanced services... it worked well:)
You create the destination table, set a null default on the column and after importing data with the dtsx you remove the default or set it to whatever you want. dtsx import will replace nulls with the default value of the column when you can't check the "keep nulls".

create table dbo.test (
 a int null
 , other columns ...
 )

alter table dbo.test add constraint x default null for a

--Run Import task here

alter table dbo.test drop constraint x