I get this pop-up error when I try to install 777 Immersion:

Installation Error: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at A.c.A(Boolean )
   at VFXCentral.MainWindow.A(Object , DoWorkEventArgs )
   at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
   at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)

 

 

Hi,

This is caused when uninstalling PMDG 777-200-300 without deleting the aircraft folder (due to installed variant in it). 
Make sure you remove your 200 and 300 folders from the SimObject/Airplanes folder or reinstall the 200 and 300 variants

Regards,