If you have deleted a user from Blackberry Manager and after a few minutes you are unable to add new users it indicates the purge process has failed.  In BlackBerry Professional they have removed the manual purge option so you need to do the following:

Open the Command Prompt and type osql -E and then enter the following commands:

1>use BESMgmt
2>select DisplayName from UserConfig
3>go

A list of users will now be displayed, note down the user that can’t be removed or re-added e.g. Bill Paxton (This example name has been added to the next step). Then run the following commands if the affected user was listed:

1>use BESMgmt
2>delete from UserConfig where DisplayName=”Bill Paxton”
3>go
1>exit