Compilation slows down when devenv.exe is called from Powershell

Hi,

 I am having the following problem. When I call VS 2012 devenv from a powershell script (or when I call a batch script from powershell), the compilation itself is executed at normal speed (it takes 15 minutes for a rebuild). But then, the devenv cmd screen close but the powershell doesn't go on immediately, it waits with very low cpu utilization for a long time (20 minutes or more).

 Anyone has the same issue?, any help would be greatly appreciated.

 Thanks!