I imaged a ubuntu 14.04 VM a few weeks ago and now can't stay logged in. When I ssh or try to login at the VM's console I y get "Connection to dncbidb01 closed". It's not an ssh problem as I mentioned, I get the same results while logged into the console. Anyone else experience this?

You quite confuse me. Is you problem "staying logged in" or "error when you try to login"? If it's the former, SSH has a server/client timeout parameter, you can google that up.

How much time passes before "Connection to dncbidb01 closed" after logging in?

It's immediate. I can interrupt the boot and get it to Advanced Options, and bring it up in recovery mode. From there I drop to a root shell and can login with root but no write permission. Nothing jumps out at me from syslog and dmesg.

rdegrado@IT-0446 ~
$ ssh -l root dncbidb01
root@dncbidb01's password:
Welcome to Ubuntu 14.04.4 LTS (GNU/Linux 4.2.0-36-generic x86_64)

* Documentation: https://help.ubuntu.com/

System information as of Tue Jun 7 09:16:34 PDT 2016

System load: 0.08 Memory usage: 1% Processes: 215
Usage of /: 22.6% of 7.49GB Swap usage: 0% Users logged in: 0

=> There are 2 zombie processes.

Graph this data and manage this system at:
https://landscape.canonical.com/

Last login: Mon Jun 6 15:20:04 2016
Connection to dncbidb01 closed.

rdegrado@IT-0446 ~
$