Hi

What kind of storage do you use?

Cheers
Michel

I use a EMC Centera as my storage  

OK, then this may be the Problem.
Is the Centera in Compliance mode, or in Basic mode?

What Service Pack of EV do you use?
There were many fixes for EV & Centera in 8.0 SP3.

I am not sure however if it is generally possible to change the Ret Cat on a Centera, even in Basic mode...
Maybe someone else could confirm this :)

Cheers

So many factors:

Centera model - Basic, Governence, Compliance
EV Centera setting - Compliance, All models, Basic
& whether you're using Centera retention categories in Gov or Comp mode.

If either Centera or EV are set to basic, all retention is managed in EV - moving between EV retention categories should not be an issue

For Centera Governence, changing retention for all items under an Centera retention category is possible (up or down)

For Centera Compliance - You can only increase Centera class retention times.

However, individual item moves between classes...basic - should be fine, or at least possible, Gov or Comp don't think is possible - you couldn't reduce an individual items retention anyway.  Extending would be possible by exporting re-archiving.

Basically - Moving between EV retention categories when using Comp/Gov Centera and not setting basic mode in EV - 3rd party Consultancy, Support, or Prof services I bet...

...I'm actually looking at the pro/cons of Centera/EV setup - at the moment I can't see any reason to stamp a retention with Centera for mailbox archiving...the data would not be seen as Compliant anyway since it could be amended before archiving.   Different for journaling though...