Have you tried calling the 'echo test' number (search for 'echo test' in Skype)? This eliminates the 'skypeout' and 'other phone networks' part of the callpath.
And the USB handset is supposed to be a normal audio device to what you are using on the computer (my guess). Have you tried recording a bit of audio from the handset and playing it back?
I have just started playing with Skype and I noticed I need to find a good microphone. Which may explain the sudden interest in microphones at work ;)
Koos van den Hout
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