Swelled battery, I didnt respond to the servicemessages fast enough. Noticed the problem only when the mousepad stopped working due to pressure from the battery. I was afraid that the Mac had suffered a lot of damage, but after removing the battery everything seemed to work ok. My mac seemed to deserve some parts investment still, but not so much as my local Mac repair shop demanded...
New battery and tools arrived after a couple of days, pretty fast for transport from the US to Norway. I have previously upgraded memory and harddrive (and removed faulty battery) following ifixits guides, so battery installment took minutes and the battery appears to be brand new (0 cycles). Very happy to have my Mac back :)
1. If the mousepad stops working, check the battery ASAP!
2. Have the right tools, those small (and for the battery, triangular) screws are a pain to work with unless the screwdrivers are the correct fit...