Hey kickbackbaz,

please take a look at your ASIO driver. You might have different driver settings:

START>ALL PROGRAMS>LINE6>TOOLS>Line6 Audio-&MIDI Devices.

Click on register tab "Inputs & Recording".

When plugged through USB the "Hardware Monitor Level" is active. When it is set to minimum, you cannot hear your POD HD when connected over USB at first. Change it to maximum level.

Let me explain: This silder exists for recording audio over a recording software. Sometimes you do not want to hear the sound that comes directly from the POD HD, you only like to hear the monitored sound over the audio software. Example: If you use additional effects on the guitar track, you do not want to hear the direct sound from your POD, you want to hear the sound with extra effects from your software.

So finally you may have to change the settings from time to time.