Random Shutdown.

[LewisGregory]

I bought my macbook in July '06.
About 1 month ago my computer had a problem and had a new logicboard put in.
After about 1 week of using it my Macbook OS X (10.4.11) is shutting down by itself, restarting itself sometimes, and when I start it up the screen flicks black for a second. This happens within around 2 hours of using it. I keep the battery charger plugged. What could be wrong? I tried the PRAM reset.

[teksurv]

I recently swapped bottom cases on my Rev. A Macbook, and I had similar shutdowns. It seems that the two thermal sensor cables were too close to the heat sink, causing an erroneous thermal event.

I suppose it is possible that throughout the use of/after logic board replacement your Macbook, the cable(s) shifted slightly. You would need to remove the top case/keyboard to check, refer to the ifixit.com guides to assist with this if you do not have Applecare. Good luck!