Ubuntu won't shutdown (stuck on "Stopping VirtualBox kernel modules")

When try to shutdown the computer it stays on a "Stopping VirtualBox kernel modules" message. It looks like it has to do something with VirtualBox, but happens even if I didn't use VirtualBox at all. Also it happens randomly.

This is what I see on the screen.

The system is going down for halt now
* Stopping TiMidity++ ALSA MIDI Emulation...

hecking for running unattended-upgrades:
* Stopping UPnP devices daemon minissdpd
minissdpd[1194]: received signal 15, good bye
speech-dispatcher disabled; edit /etc/default/speech-dispatcher
* Stopping VirtualBox kernel modules

And it stays here forever if I don't do the "force power-off".

My specs: Ubuntu 12.04 LTS on Dell Studio 1555 Laptop

I think I found out what's causing this. It must be Apache or something, because if I stop xampp before shutdown, it all goes well. Unbelievable.