Ex2007 public folders problem   

I have migrated from Exchange 2000 to Exchange 2007. Everything works fine 
but I can't change the permissions in a public folder neither remove 
permission nor add permissions. I get an error like:  'You can't change the 
table property MAPI.NET'.
I tried with a new public folder (created directly in ex2007) and the 
behavior is the same.

Does anybody know what it is happening?

Thank you in advance.

date: Fri, 30 Nov 2007 09:24:52 +0100   author:   manuel