What model of GW do you have at each site?  SRST numbers are limited by router model.Whats the Wan connection for each site?  MPLS?  QOS?How many of the 30 will need to be on calls at the same time?

We have this issue once in a while.  The thing I found fixed it was to right click the task bar and choose cascade windows.  This does cascade all open windows, but the CAD application does show up.  PITA, but for a few times a year fix it works fine...