PVD isn't running anything in the background, and it running or not isn't likely to have anything to do with MC crashing. In order to use PvdImport, you installed Firebird—which should be running in the background or as a service. If anything, it not running might cause PvdImport to cause a crash. There's a Firebird Server Manager applet in your Control Panel. Check that to make sure the server is set to run as a service and to start automatically.