This hit me today. One of my old migrated distribution group lists wouldn’t work and when I went to edit them I got a ‘Validation Error This field cannot be empty’ when I tried to edit the members of the distributions groups.
Found the solution in the SBS 2008 newsgroups:
1. Open adsiedit.msc and connect to the Default Naming Context.
2. Expand Default naming context -> DC=domain,DC=local -> OU=MyBusiness ->
3. Find a group that was created post migration and view its properties.
Look for msExchVersion = 4535486012416. (Verify if the number list matches
this one or not. I suspect it will, but want you to be sure.)
4. Now go view the properties of a migrated group and look for
msExchVersion. It may not be there or it may be empty.
– If it’s empty, set it to the value 4535486012416 or whatever the group
you found in #3 was set to.
– If msExchVersion is not there, you may have to click the Filter button
and alter the settings to see if it’s not set to appear.
5. Once you’ve set msExchVersion to the appropriate value, click OK out and
then try your edits to the group.
Sure enough, that was the fix.