HID bulb arcing in socket

A couple weeks ago I noticed the passenger side headlight would turn off almost immediately after I turned it on. After a couple hours of swearing at it/trying to twist it out, I finally pull the bulb and socket out of the metal retaining clips in one piece. I had to use a couple channel locks to get the bulb to twist out of the socket, and when I finally did I saw the socket and bulb were very toasty.

I cleaned up the socket, replaced both bulbs, and everything seems to be working fine so far, knock on wood. Has anyone else has seen this kind of arcing between the bulb/socket? If this is a one-time thing, great, but I'm wondering if it's symptomatic or problems someplace else.