*Disclaimer* This is a different model MBP than my own. It may be a COMPLETELY different issue. This is just my experience with what seems to be a similar problem.

Hey man. I had/have a similar problem with my a1260 mbp 15" (with so much surgery performed on it its basically like Joan Rivers. Major parts replace once, graphics card recall, entire top half replace...all different incidences). It became so bad (a little bit after the top half and a memory upgrade to 6gb) with the sudden shutoffs that I couldn't boot it up anymore. Battery in, battery out, charger in, positioned vertically, at an angle (read on for that fun bit), being very gentle with the CPU load...you get the idea.

However, before it became that bad, I noticed something odd. If I kept the laptop propped up by putting something that was about the thickness of two fingers put together at about the battery area, it would stay on (sometimes).

Now the bad news. The ability to change the behavior with changing the position made me think it was a short or a contact issue. I did some poking around and noticed that certain pressures on the power button of the top-case would cause the shutoff. Again, sometimes, and the pressure was not always necessary. It was some kind of short I believe. However, after running a stress macro, the problem showed its ugly head again. I tried going back to 2gb ram. I tried a number of things. Every time, the same issue.

I said "frack it" and brought it into someone a bit more knowledgeable than I, my local repair shop. They opened it up and almost immediately suggested that it was the left i/o board, citing that it may be an issue with the way power is distributed from the battery/charger. They replaced it, sealed the laptop up and ran into the issue. They then called and asked if I wanted to replace the I/O board in my (going on) 5 year old MBP, an $800+ repair in a machine that-while it has served me faithfully for those five years-has required WAY more than I purchased it for in repairs.

I'm now wondering if I can scrounge the board from another MBP somewhere in the world/my local sphere, live with the problem, or...perhaps buy a new laptop. Perhaps one that isn't so crazy expensive to repair or replace parts. I only hope that laptop supports Lion. :(

So here's the long and short of it Chris. The problem became so bad I would only hear the boot noise and then it would shutdown. A replacement top-case (ie the part with the speaker-holes) fixed the problem...sorta. I haven't spent any real time with it since that fix, I basically turned it on, used it for a couple of days intermittently (I have an iMac and another MBP that I had pretty much switched over to when this problem became unmanageable in october), suffered the problem again and took it in. I'm not sure if the total fix is replacement of the Logic Board, but the repair shop certainly thinks so.

Sorry buddy. But look at it this way. My laptop is from 2008, yours 2007 if I'm right. They're old man. It really sucks, but it may be time for us to replace our laptops.

Hello there, it's been a while since I've access this site. Allow me to comment on this OLD matter that you had (assuming that you have resolved the matter by now), you know a lot these earlier Macbook pros appear to have this "common issue" that was never fully explained and although there are a lot of other factors that can contribute to the cause (compounding the initial problem) it would serve all users (who have these machines) to ensure that they have NO 3rd party software that the machine sites as a problem (by means thru the system profiler-Logs-Kernel log). Take the time and look thru the listing and see if you can identify any programs there that appears to be a problem, another way is to update all of your programs individually. Macs are very specific with their programs and there are some 3rd party software can give it problems you wouldn't expect and investigating this issue more deeply requires a lot of time and patience, it's not ALWAYS a defective logic board (now yes they can go bad i.e., certain components starts to "break-down" becoming erratic). Now here's food for REAL thought: if your machine has been opened up a few times you will want to look for any type of small problems that looks -huh: screws, single small wire strands, "dried" traces of spots between solder points of other components or exposed signal paths. Now, the thermal compound that is on the processors and video card can be a problem also. It has been said that the compound does not conduct electricity between solder points, I have found that when you find thermal compound that has spreaded to close to (touching) other solder points from the case of processors or video card I suggest that completely remove that compound from those components and the heat sink as well. Reapply fresh "Ceramique 2" thermal compound (it MUST be applied properly) to the components ONLY-not the heat sink, make sure you have examined it carefully for any type of distortion/stains before reassembling. This just my suggestion for you to consider, I know it will be time consuming but if you have the time to invest I suggest that you consider it.

I forgot to reply to this thread. I took the lid of my MPB prodded the flat flexible connectors, decided it was too big a job to get to the temperature sensor so put the lid back on. Not had a random shutdown since.

Great, but don't get too happy just yet. Just watch it and see how it goes, I've seen this kind of temporary success before.

My logic board had to be replaced. Bummer, but it works completely now.