My ZTE MF627 dongle seems to have issues with windows 7, but once I actually sat down and had a look, things turned out to be much simpler than expected…

Simply manually install the troubled drivers For me the drivers were located:
C:\Program Files\ZTE_MF6X6_USB_MODEM_1.2050.0.6\drivers\32bit\VISTA
C:\Program Files\ZTE_MF6X6_USB_MODEM_1.2050.0.6\drivers\64bit\VISTA