For Act! users, a memo field (aka notes) field is useful to add to the top half of your contact screen.  This allows you to have an important message that doesn’t get lost in history.  If you want to write a note that requires to press enter between lines, it won’t respond.

The solution is to press CTRL-Enter to get the line break between lines.  Memo fields behave a little differently than standard notes or history in Act!.