It may not be a software problem. Have you tried scanning with a rooftop antenna first? You may not be able to pick up a signal with the supplied antenna. Also, is the USB tuner purely digital or a hybrid (digital and analogue). If the USB Tuner is purely digital, check the that the software is on a digital-only setting.
Off the top of my head, I cannot think of any free s-ware, the one supplied with the stick should work fine.
Not having used Blaze myself (I use HyperMedia on one machine and MegaSky on another) there should be an option to scan and then rename the channel numbers so that a re-scan is not required.