<< When I try:

Q.Params[0].Clear;

I get the following exception: Invalid date/time format [no error code] >>

As a last shot, try:

Q.Params[0].Value := Null;

If you get the same error, I'm out of ideas ;-)

<< Also, Where is NUL defined? >>

NULL (not NUL) is defined in Variants.pas (D6/D7) or System.pas (D5).

Ole Willy Tuv