Index: ehci_pci.c
===================================================================
--- ehci_pci.c	(revision 186493)
+++ ehci_pci.c	(working copy)
@@ -315,6 +315,14 @@
 			device_printf(self, "Quirk for CS5536 USB 2.0 enabled\n");
 			break;
 		}
+
+		/*
+		 * Quirk for Parallels Desktop 4.0.
+		 */
+		if (pci_get_devid(self) == PCI_EHCI_DEVICEID_ICH6) {
+			sc->sc_bus.usbrev = USBREV_2_0;
+			break;
+		}
 		sc->sc_bus.usbrev = USBREV_UNKNOWN;
 		return ENXIO;
 	case PCI_USBREV_2_0:
Index: uhci_pci.c
===================================================================
--- uhci_pci.c	(revision 186493)
+++ uhci_pci.c	(working copy)
@@ -389,6 +389,12 @@
 		break;
 	}
 
+	/*
+	 * Quirk for Parallels Desktop 4.0.
+	 */
+	if (pci_get_devid(self) == PCI_UHCI_DEVICEID_ICH6_A)
+		sc->sc_bus.usbrev = USBREV_2_0;
+
 	err = bus_setup_intr(self, sc->irq_res, INTR_TYPE_BIO,
 	    NULL, (driver_intr_t *) uhci_intr, sc, &sc->ih);
 	if (err) {