apt-get upgrade - why is " lmce-mediatomb" and "pluto-website-admin" kept back ?

[Viking]

# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  lmce-mediatomb pluto-website-admin
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.

root@dcerouter:~# dpkg -l pluto-website-admin
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name           Version        Description
+++-==============-==============-============================================
ii  pluto-website- 2.0.0.44.10080 <insert up to 60 chars description>

root@dcerouter:~# apt-cache policy pluto-website-admin
pluto-website-admin:
  Installed: 2.0.0.44.10080223227
  Candidate: 2.0.0.44.10100623324
  Version table:
     2.0.0.44.10100623324 0
        500 http://deb.linuxmce.org intrepid/lmce-alpha-latest-updates Packages
*** 2.0.0.44.10080223227 0
        100 /var/lib/dpkg/status
     2.0.0.44.0901260810 0
        500 http://deb.linuxmce.org intrepid/lmce-alpha-latest Packages


# cat /etc/apt/preferences

# We take MythTV from our repo always
Package: mythtv mythtv-frontend mythtv-backend mythtv-common mythtv-database mythtv-transcode-utils mythweb libmythtv-perl libmyth python-myth mythtv-themes mythplugins mytharchive mytharchive-data mythbrowser mythgallery mythgame mythmovies mythmusic mythnetvison mythnetvision-data mythnews mythvideo mythweather mythzoneminder myth-doc
Pin: origin deb.linuxmce.org
Pin-Priority: 1001

# If our local package uses the same version as elsewhere, we take the one we have locally.
Package: *
Pin: origin
Pin-Priority: 500

[Marie.O]

http://lmgtfy.com?q=difference+between+apt-get+upgrade+and+apt-get+distupgrade