Lighting, Light Fixtures, Ceiling and Exhaust Fans - Outdoor Fixture Problem

I have some outdoor carriage lamp-style fixtures (Royce Lighting) that I purchased from Lowe's a couple of years ago. I have had to replace one of the units already as it began to 'cook' the bulbs for want of a better term. The bulbs would turn black and literally the tips of the candelebra type bulbs would crack and blow off. Finally, the fixture started blowing the circuit breaker if there were bulbs in the sockets and the switch was turned on. I replaced that fixture last fall. Now, a second fixture has developed a problem. I went to replace a burned out bulb the other day and discovered that the burned out bulb actually has a hole burned through the metal base of the bulb. Obviously there is something wrong with the socket. Has anyone else experienced something like this? Any other experiences with Royce Lighting? I wouldn't think environmental conditions should be a factor as these fixtures are intended for outdoor use and I have them mounted on the pre-existing electrical boxes outside my front door and garage doors (I replaced ugly old fixtures with these, in other words).

Any thoughts?