This is an older version of WirelessUtility that should work with OS X Snow Leopard & Lion, although not recommended for use with Snow Leopard. Tested on Ralink RT3090.
Note: Before you install this file, make sure you have already installed the corresponding app according to your card from here:http://www.ralinktec...port.php?sn=502
This file is meant to replace the WirelessUtility.app located in the /Applications/Ralink Wireless Utility folder that is installed as a result of installing the .pkg in the link above. The "Device not found" error could be a result of not correctly installing the kext included with the .pkg from the Ralink website.