I almost dread saying this, but here goes.
Check the voltage from each leg to neutral and make sure it is the same. The safest way to do this is by checking at two outlets that are on different hot legs so you don't have to open the breaker box.
If the voltages are not the same (within a few volts), there is a good chance of an open neutral. Maybe at your service point, maybe at the pole. See if you can get a somewhat unbalanced load between the hot legs when you do the voltage checks. An electric heater would probably do the trick.
If this turns out to be the case, please call a competent electrician in to troubleshoot it.
Or it could be a batch of bad bulbs.
BTW, if you want to continue using incandescent bulbs stock up now. A provision in one of the 2000 page bills passed last year that no one read bans them in a couple years.