I've seen quite a few microwaves that had blown fuses for no apparent
reason. There's a chance of an intermittent problem, but it is
probably fine. If it blows again, there is a definite problem that
needs to be repaired. A 125v fuse is fine as long as it's a 120v
microwave.



I've had the same experience, microwaves are the only appliance I've
ever encountered where replacing the fuse will truly fix the thing many
times. I think the interlock occasionally will stick for just long
enough to pop the fuse.