Synonym, Drop & Create OK, create or replace NOT OK, Why?

Hi all
I have a synonym created on a remote database SYN_REMOTETABLE.

I have a pl/sql program has a line like this
Declare
var1 SYN_REMOTETABLE.MyCol%Type;

Now I recreate the synonym using
CREATE OR REPLACE SYNONYM SYN_REMOTETABLE connect to ......

The program does not compile.

Next, I drop the synonym and recreate it using
CREATE (OR REPLACE ) SYNONYM SYN_REMOTETABLE connect to ......

The program compiles.

Any insights whats happening here. Even before the program compiles when I do "Select * from SYN_REMOTETABLE" it does work.

Sridhar