Strange:

I issue this

DECLARE @val CHAR(4)

If @val = NULL

select 'Yup1'

else

select 'Nop1'

SET @val = NULL

If @val = NULL

select 'Yup2'

else

select 'Nop2'

there is a result:

----

Nop1

(1 row(s) affected)

----

Nop2

(1 row(s) affected)

?