I am very interested in this. Did you ever get a solution? I am running an APC UPS and didn't pay any attention to it when I did a clean install (I did get a battery icon though) What (if anything new) have you discovered about UPS and Vista?
I have an APC UPS and it was immediately found during installation with no extra drivers and even has tests that Vista runs on it every so often to check its status. Pretty nice. Did your UPS come with any software? Possibly a hardware driver/software app issue if Vista is not recognizing it already.