updates on 9.04

[Stan Hughes]

Hope I am not making a pain of myself, but here is another question following 
installing 9.04 on my computer.  Formerly I was using 6.0whatever (dapper 
drake) and the updates available would appear on the on the bottom panel and 
were very easy to install.
  In 9.04 I get a notice that 12 updates are available.  When I click on it 
says "4 security updates; 4 blocked updates".  That doesn't add up to 12.  How 
should I be getting updates?  Why would it tell me about blocked updates and 
why would they be blocked?  Am I going about this completely wrong?

  Thanks for your help.

          Stan