Has anyone every seen this and does anyone have a solution?

Often, if I'm running by VBA code, if I switch to another application
during the process where Excel is opening files and copying data into
arrays in the program, it stops. I've noticed that this doesn't occur
as I start the program, but during it.

Also, if I switch to another application and then come back,
even the code continues to run, the Application.StatusBar stops
updating, even though I know its receiving updates. It doesn't stop the
program, but it does give the user the perception that it has stopped.