Newbie to SID: How to install the previous version of a package ?

[Sylvain Vedrenne <sylvain.vedrenne@free.fr>]

Hello,

How to install the previous version of a package ?

Example:
I want to install gnome-session,
apt-get install gnome-session  complains that there is a grave bug in 
desktop-base version 0.3.13 - see below details from Debian-BTS. So I decide 
to install later...

  - Is it possible to install gnome-session using the previous version of 
desktop-base: version 0.3.12 ? 
      - How to do that ? 
      - Is it safe (as far as it can be in Sid) ?

Cheers, 
Sylvain.

"
#244649: desktop-base: installation not possible due post-removal script
Package: desktop-base; Severity: grave; Reported by: martin krung 
<kd.089.ch.7LO.df_f.df_ddf.com.t@gmx.net>; 
Tags: sid; 
Done: mark heily <mheily@yahoo.com>; 
Will be archived: in 26 days.
"
By the way this bug is "Closed" according to 
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=244649
So should I ignore the grave bug message returned by apt-get install ?
I really hesitate...