I have a user that I can't activate the her account on our BES. I beleive it has something to do with her account, but I have verified that her settings (groups, besadmin account rights, etc.) are the same as other users.
When I try to activate on any device she receives the network email, but it does not remove the email from her mailbox and the activation eventually fails. I have verified that she has the enterprise data plan, and I have also tried activating her account on my BlackBerry and it still did the same thing.
I've seen situations where the only way you can get a device to activate is to remove it from bes and add it back.....don't know why exactly.....these devices have followed the pattern you describe, network message arrives but never vanishes..the other thing that I've found will work sometimes is to give them a static mailbox agent....