I rarely use staging areas but I did today and I could click all the units I wanted but it would only dispatch 10. The red German error page would come up as it dispatched them. If I selected less than 10 everything was fine. An alliance member said that this happened to him the last time he used a staging area but it didn't this time.
Also, not sure if this is an error or should be a suggestion, but the loading dispatch time (for 10 units) is significantly longer for staging areas than dispatching 70 units for a call!!