Lab Manger Login Error: The username -whatever- already exists in vCenter Lab Manager. Please ask your Administrator to delete the previous user account.

A user called me with this error, I had never heard of it before, but here is what happened. The user left the company, I disabled his account.  He was rehired by the company, so I re-enabled his Lab Manager account.  However, his AD account had been deleted (by company policy) and he had been generated a new AD account with the same login name.  LBM was smart enough to know that this was not the same account and gave me a valuable error message.  I deleted his LBM account, recreated him and was ready to roll.