I had the charger plugged in.

But I think the bug is because N900 when re-booted via power-menu "Reboot"-command does not mount /dev/mmcblk0p1 for some reason. And if recaller has its destination directory (/home/user/MyDocs/recaller/) set to place which does not exist, it starts recording when a phone call comes, but gots messed up because there were no destination directory, ....so the system bug caused a recaller bug.