Dave: if all the lights do not work I would sooner think a fuse or wirering problem to the first fixture in this line of bulbs, then burnt bulbs
If fuse is known to be good and the power is getting though to bulb side of fuse, for a test I would run a direct wire from here and splice it into the first fixture in line. If this works I bet the rest of the lights will work too with this jumper wire in and your problem is either the ground or power wire from fuse to first fixture.
Gerry