Packages being kept back after security notices

[Lesley <lesley.binks@swallow-soft.co.uk>]

Hi

I hope someone can help.  With no intervention from me I get the 
following on an apt-get upgrade after an apt-get update

The following packages have been kept back:
  icedove openoffice.org openoffice.org-base openoffice.org-calc 
openoffice.org-core openoffice.org-draw openoffice.org-evolution 
openoffice.org-gcj
  openoffice.org-gtk openoffice.org-impress openoffice.org-java-common 
openoffice.org-math openoffice.org-writer python-uno

after
[DSA 1307-1] New OpenOffice.org packages fix arbitrary code execution
and
[DSA 1305-1] New icedove packages fix several vulnerabilities


Why would these packages be kept back?

Apologies if this is the wrong place to post this question

Regards

Lesley