A server I am maintaining stopped during boot on the "Stopping userspace bootsplash" or "Configuring network interfaces". If Ctrl-Alt-Del was pressed the machine rebooted so it was not completely stuck. I tried booting in rescue mode and checked the /etc/network/interfaces syntax but no problem visible there.
The solution was quite simple. Boot in rescue mode and select package repair. After repairing my packages the machine was rebooted, then fsck was ran automatically (which took quite a while). After that the machine booted normally.