Both of your tasks with the BBB resource assigned have an As Late As Possible constraint. Project cannot level tasks in a project scheduled from a start date (which yours is) that have ALAP constraints.

If you truly need BBB to perform both tasks, then you'll need to drop the assignment units so the sum is less than or equal to the resource's maximum units.

See the Notes section in the follow Microsoft article:

http://office.microsoft.com/en-us/pr...241.aspx?CTT=3