If you ever find the Dynamics CRM 2011 Explorer / Tools options missing from within Visual Studio 2010 ....

... check prerequisites are installed:-

1. Visual Studio 2010 SP1
2. Silverlight 4
3. Windows Identity Foundation
4. CRM Developer Tools (found within the CRM SDK, Tools folder)

Then check that the following is mentioned in your solution file (if you open the .sln file in a text editor):

Save and reload the solution in Visual Studio 2010 - everything should now be back!

Having backed up a CRM 4.0 Organisation database, and restored it into a CRM 2011 deployment, we attempted to use the "Import Organisation" feature of CRM Deployment Manager to import and upgrade the database.

Stepping through the "Import Organisation" wizard, we got to the "Map users" screen, where we expected to map the Active Directory users from the source deployment to equivalent users within this one. 

At this point, the  import wizard just hung. We waited a few days....still nothing, it was stuck on the same screen.

The install log, crm50dmsnapin.txt, revealed this error:

Exception occurred while mapping usersMicrosoft.Crm.CrmArgumentException: Expected non-empty string. ---> System.ArgumentException: Expected non-empty string.
Parameter name: domainAndAccount

To fix this, we ran the following SQL against the Organisation database we were trying to import:

update systemuserbase
set DomainName = 'domain\user'
where isNull(DomainName, '') = ''