Deleting grouped email

I often group email by name, subject, date, etc. A week ago, I could delete
the group name (the blue line with the +/- on it) and press the delete key,
which would delete all email under that group. This no longer works. I am
using Outlook 2003 SP2, part of Microsoft Office Professional Edition 2003. I
was not in the office for the intervening week. To my knowledge, the only
change was the application of a new version of Enterprise Vault.

Thanks in advance.