return key adds code and then goes to next line

Does anyone know why the return key seems to be almost double tapping? When I start to enter a line of code and the program picks up on it I use the return key to select it but since yesterday afternoon it seems to select the code as it should but then it drops down to the second line before I can add more data or even a semi-colon. This is happening on two different computers. My Macbook pro and my iMac. My preferences are greyed out so I cannot go into that.  Anyone else notice this or know how to fix it?  Thanks.