I have the same issue and worked with my IT department to trace it down to this problem:
http://motorola-global-portal.custhelp.com/app/answers/detail/a_id/39440/kw/39440/session/L3NpZC9vYVNOMmg4aw%3D%3D
Essentially the exchange security policies work for android 2.2 on all phones except the motorola droid.