That just happened at my house. The problem for us was the family of raccoons living under the house. They messed up the wiring. No worries, we humanely trapped them and they were let go in the woods miles away. :)
If it's an older home it's possible that they shared the same lost neutral. An electrician can test the hot to ground and if it's hot to ground then the problem is either the neutral is bad or the device on that circuit is defective. Another possibility is that the house is wired with aluminum wire that expands under load and contracts when it cools. Eventually it will expand and not contract thereby causing the circuit to fail. You can check the box for aluminum wire and if it is you need to check it by tightening the terminal screws then reenergize the circuit breaker to see if it is I one or both devices.