Probably has a conflict with Vista and uPnp. Have you checked to see if you have the latest firmware for you spedstream. Remember Vista is new and there are still some products that may need to have there drivers and firmware upgraded. Some products still do not work properly with Vista. You can find a link to the firmware on the left hand side of the page in the link below.
Siemens AG - FAQ's: 4200 & 6520