Are you sure the cable is good? Try deleting LG USB drivers and re-installing. Once installed, reboot computer to allow the other two drivers to install (there are 5 in all). Then plug phone in after reboot to finish install.
? Do you have the Android SDK ( with the tools and platform-tools folder) and the Java jdk-1.6u45 installed on computer? Do you have path to adb.exe set, and the "class path" to the java.exe set?