The beta has pretty much worked smoothly until today. I updated FSUIPC to the most recent build (4.961) and now I get this error on startup of VOXATC no matter what flightplan, voices and aircraft are chosen for a flight:

Log Start 02/01/2017 19:45:06

Collection was modified; enumeration operation may not execute.
   at System.Collections.ArrayList.ArrayListEnumeratorSimple.MoveNext()
   at com.intworkings.bglafd.WorldGridCell.ReviseAirports(ArrayList airportsForRevision, BGLAFDAirport baaIn)
   at com.intworkings.bglafd.WorldGridCell.ReviseAirportComponents()
   at com.intworkings.bglafd.WorldGridCell.GetAirports()
   at com.intworkings.bglafd.BGLFile.GetAirports(Double lat, Double lon, Int32 index)
   at com.intworkings.voxatc.Chart.AddAirports(Position posIn)
   at com.intworkings.voxatc.Chart.LoadBGLPositions(Position pos1, Position pos2)
   at com.intworkings.voxatc.Dispatcher.SetFSFlightPlan(String id, AircraftType atIn, MFSFlightPlan mfsfp)
   at VoxATCServer.VoxATCServer.SetupMFSFlightPlan()
   at VoxATCServer.VoxATCServer.InitVoxAtc()

This is with P3d V3.4 Hotfix 2.

As an aside, this error disappeared for me with P3d HF 3 and FSUIPC 4.962, so I'm assuming that it was specific to my setup.