[ubuntu] Cant upgrade Virtualbox on Ubuntu 14.04.1

I have Ubuntu 14.04.1 running Virtualbox 4.3.10-dfsg-1 that was installed from the repos. I have started having problems with one of my vms (Utopic) and noticed that the current version of Virtualbox is now at 4.3.16. I followed the instructions on the Virtualbox web page for adding the deb entry to my sources.list, but it still won't upgrade. Synaptic still shows 4.3.10-dfsg-1 as the latest version, and if I try to install it using the Software manager it tells me that it will break currently installed package virtualbox. . .

So, my question is this. If I use synaptic to remove (NOT completely remove) my currently installed 4.3.10-dfsg-1 version of VB, and then re-install the 4.3.16 deb from Oracle, will I lose all of my virtual machines or will they still be preserved?

Thanks,

Wayne