Janesville police are investigating an attempted robbery of a fast-food restaurant on the city’s north side.  Police say the attempt occurred at the Culvers on Milton Avenue early Thursday evening.  Officers say a man in a red four-door jeep came through the drive-thru and gave the attendant a note demanding money.  While a number of workers gathered to review the note, the would-be robber drove away.  Police say this attempt is very similar to a robbery at a Culvers in Lake Mills late last month.