I've been experiencing the following problem with my late 2007 MacBook Pro: I can't use it on batteries. As soon as I disconnect power supply, it works for 10-15 minutes and switches off. Not sleeps, but suddenly turns off completely. The system battery indicator drops by about 10% (showing 85-90% battery charged), whereas 4 out of 5 LEDs are lit on the battery itself. After such a sunned switch-off, I'm not able to start again the laptop - it doesn't react on Power On button - like the battery wasn't inserted at all. Right after I plug on power supply back again, everything gets back to normal and I can use it normally, but still only if it's connected to the electricity. So far, I didn't care much about it, as I used my MBP mostly at home. Only recently I realised I have to solve the issue, as more and more often I need to work on the laptop away from home and it's not always possible to carry power adapter with me. I already tried a couple of solutions found in the Internet for similar problems, including deleting some preferences files, resetting PMU and PRAM, but nothing worked for me. I wonder if anybody encountered something like that. If I'm able to work on my laptop using power supply, maybe it's just a battery fault and replacing it would solve the problem. Or maybe I need to visit a professional Apple service although I'd like to leave this as a final solution as I need to work on my laptop on a daily basis and in my country technical service is outsourced to other companies which are infamous for being very slow.