What version MiCollab?
Prior to v8, the AD password sync between client and desktop didn't seem to work very well when the AD password was changed: some time after the AD password changed (minutes to hours), the client would spit the dummy and then for 10 minutes to 3 hours it would refuse to accept the new password. Eventually it would sync again and be happy.
I recently tested an AD password change on v8 and it was seamless.