1. Most likely the capacitors in the fixture's ballast held a bit of a charge, enough to power the bulb for a fraction of a second. I wouldn't worry about this.

2. I have had CFs crack, though I don't know the cause. It is pretty rare, in my experience, but it does happen. Yours might be an especially cheap brand (just guessing). Again, I don't think it's a particularly big deal.

Make sure you dispose of the cracked lamp properly. I put my spent CFs in a box on a shelf in the cellar. When I have enough of them to make it worthwhile, which is every few years, I take the box to my local household hazardous waste disposal site.

Thank you for the reply, David. The bulb was from Sylvania, so it is not really a cheap brand. But I understand cracks happen. Maybe it could be from my handling, but I am not sure.

I'm still a little bit concerned about overheating. I had turned it on for only about an hour or so before that happened. The other lights were all working fine. Maybe the protection logic in that can is more sensitive than the others. I guess it should be okay as long as it was not caused by a bad wiring or some other problem.

Thanks again.

Well, CFs don't generate much heat, so I don't think overheating is too likely to be the cause. I suspect (but of course I can't prove!) that your bulb cracked because it had a factory defect.

If you had the lights installed fairly recently, you might call the contractor and ask about exchanging the cracked bulb for a new one.

Oh, I was talking about overheating because the light initially went off w/o cracking the bulb after being turned on for about an hour. I was guessing it was due to the thermal protection of the can. Then, as you mentioned, CFL doesn't generate much heat and I was wondering if it is normal to go off after just one hour of use (I have 8 installed and only one had that problem) or if it implies any problems in installation or material itself.

The bulb got cracked after I turned on/off the light a few times after the incident.

I see a couple of possibilities. One is that the ballast in that one can is overheating; another is that the thermal protector is a little hypersensitive.

Try it for a while with a known-good bulb. If it continues to act up, I'd say tat since it's a relatively new installation you should drag your contractor back to the house and tell him or her to make it right.

Are the CFLs labeled for base up if they are in a can light?

While they do not generate a lot of heat, most of the heat is generated in the electronic ballast in the base of the bulb.

Not all are designed for base up operation.

Brick, if I'm reading the OP correctly, these are CF cans, not retrofits. The ballast is in the can, not the base of the bulb - I think.