Hi,
I had the same problem, you could try to download the drivers from here: http://ftp1.digi.com/support/driver/40002636_A.zip
This are the drivers for the XBIB-U that are for windows XP, but they work well on vista home premium(32-bits), also to fin new drivers you should try to look on the support tag, then select the product X-CTU, because you could use the XBIB-U to work with the X-CTU and to do that you need the usd drivers