I swear I am not trying to Spam the forums, but I have seen this 10.5.5 battery issue here and at the Apple Forums. Here is a cut and post of my post at Apple: Since updating to 10.5.5, when running my 1st Gen 2.16 gig Core Duo 17 inch MacBook Pro off the battery, at around 13 to 15% remaining on the battery, the machine just cuts out. Turns off, acts as though it has lost power completely. Poof and off. No low battery warnings. No shutting down. It's as if the battery as been removed, though it has not. Push the button on the battery and a light and a half illuminate. The only way to get the machine back on, is to plug it in. At which point it turns on with no action from me (this may be because I have it set to turn on after power failure). I have also noticed, while plugged in and charging, with less then a 15% charge, if I unplug it, it loses all power as well. More than a 15% charge and I unplug, it stays on until it drops below 15% or so. I have reset the SMC, and still no joy. I have found this link: http://support.apple.com/kb/TS1970 but it doesn't really apply, as i have the the battery status in the menu bar (have since I got the machine) and it doesn't go to sleep (just turns off) to make the battery calibration work. And I usually re-calibrate the battery ever 6 weeks or so anyway. As I said, this starting happening today. Just a day or so after I updated to 10.5.5. Is this a bug in 10.5.5 or is 10.5.5 the victim of a horribly retched coincidence of bad timing due in part to the machines 26 month age? I love this machine, she has been trouble free, even through the initial 10.5 upgrade. An extremely reliable work horse the never acts up. It's weird, but til now... she has operated flawlessly. I got pretty luck with it. I would hate to have to replace it. Now, please don't dismiss this if it hasn't affected you. The range of machines and software running on those machines is gonna make this difficult to track down. It certainly has affected me. I am sure there are plenty of people lurking here who had perfectly fine batteries on Monday, only to discover their batteries have go the way of the DoDo come Tuesday. I can only conclude this is a software issue. Not hardware. And it sucks! Again, not trying to spam the boards... I just want it made clear that this 10.5.5 battery fiasco is more wide spread than some may think. Thanks for taking the time to read my post!