It was working fine until the update was installed, now it won't launch.

How do I get the 'old' version back?

I was finally able to get support from the Canadian branch of Plantronics tech support team. I was finally able to remove this application from my computer and I am no longer plagued by the app popping up each time I launched iTunes.

Here are the instructions that hopefull may help others remove this annoying situation. FYI: the instructions on their website never referred to a folder named HAL:

Make sure the user is looking in the correct folder - that at the system level instead of the user level. In Finder ensure you navigate to /Library/Audio/Plug-Ins/HAL/VolumeLogic.plugin by first clicking "Mac Hard Drive", instead of searching under the login name space. (It sounds like she is already looking in the right place and it isn't there, but it's best to check. These folders exist in two places on a Mac.)

If there's no Volume Logic listed in the HAL folder, it could be that this user instead has the original broken VL installed. (I'm sure it's still available from a 3rd-party link somewhere.) I'd suggest asking her to try checking the /iTunes/iTunes Plug-ins/ folder for VolumeLogic and deleting it from there (as per the old iTunes uninstall instructions available from TAC.)

The actual VL plugin on the Mac is named "volumelogic" followed by either ".app" or ".plugin". Searching for just volumelogic in Finder should hopefully find the file to delete.