chroot fails into kubuntu system

[Xen]

Hey,

I am trying to chroot into an installed Kubuntu system. Version is 15.10, 
just before the beta. I have tried both from Kubuntu Live DVD (that 
installed the system) and from OpenSUSE 13.2 installation.

I get the error:

chroot: failed to run command ‘/bin/bash’: Permission denied

Actually any command executed by way of the chroot will fail:

chroot: failed to run command ‘/bin/true’: Permission denied

The volume is mounted without any noexec or user:

/dev/mapper/linux-kubuntu on /mounts/kubuntu type ext3 
(rw,relatime,stripe=16,data=ordered)

I can chroot fine into the OpenSUSE installation, even from the Kubuntu 
Live DVD. The mount is a thin-provisioned volume. That is the reason I 
need to chroot into it, because Kubuntu won't start.

For a test I am copying the installation to another partition outside of 
any LVM. It is a primary partition. The same problem, so it can't be 
related to LVM or thin.

What is the problem here? Why can't I chroot into that Kubuntu install?.

Regards,

B.