I've got Oracle VirtualBox 4.2.10 installed on Ubuntu 12.04, and with evry virtual machine I create, the "host key", which is supposed to release the mouse doesn't do anything. I've already installed the Guest Additions Expansion Pack (or whatever it's called,) and that didn't fix it. What else should I try?
P.S., not a duplicate of Question 291101 - that one is in Windows 7, this one is in Ubuntu 12.04. The answer to that one is inapplicable to this one.