OS 10.4 - Crash Issue?

Not sure if this is a software crash issue or a hardware issue but...

Last night I was surfin' the web, testing my new DSL line. I set the MacBook down and walked away for a few minutes. When I returned it appeared to be asleep but when I tried the trackpad and keyboard to wake it up -- nothing. The screen didn't so much as flicker nor did the fans spin up. So, I press and hold the power button while watching the power indicator on the front. It goes out and I press the power button again. This time the indicator lights-up, but no screen, no fans, nada. Hmmm.

I waited a few minutes and tried again, same thing except this time the screen flashed gray and went out. I removed the power cord and the battery and did a PMU reset and let it sit about 10 minutes, replaced them and powered it on again. This time it booted fine. A little while later, it happened again. Went through the same process to fix it. I haven't used the machine yet today so I don't know if it is fixed.

The only thing that has changed on the machine is that I ran the AT&T DSL installer CD to configure the DSL line, but it ran fine for a couple of days.

I'm not sure which log to check for this kind of thing.. any suggestions?

The MacBook is about 1.5 years old, gently cared for, and I do have Applecare so taking it in isn't a problem.