I get nice full wave forms in Reaper on my Windows 7 machine with my POD HD500.
Are you using the neck pickup in your guitar? Have you tried boosting the mixer level settings on your patch?
Any chance you could attach your patch to this thread so I can check it out?
Have you resolved this issue? I posted this issue in the Line 6 Recording section today. I am using Logic Studio and also cannot get a useable level from my HD 500 using the USB Audio interface.