I have searched, and I could not find any upgrade for Mt. LIon on a reliable site. I doubt that the driver you have is compatible with Mt. LIon, And I could not find an uninstaller either. If you do not have the installer CD mentioned in the help, it will be complicated to uninstall.
I downloaded the installer and looked what it will install. It really does not contain any option to uninstall like earlier versions.
The files will be installed all over the place in your System Library. I am sure the Kernel extensions
com.digidesign.iokit.DigiDal Version: 9.0f4
com.paceap.kext.pacesupport.snowleopard Version: 5.7.2
are installed by this driver (probably in /System/Library/Extensions/) but for sure you will also find files in
/System/Library/LaunchAgents/
and
/System/Library/LaunchDaemons/
and
/System/Library/StartupItems/
I cannot advise you which files exactly need to be uninstalled, because I do not have this driver on my system and by simply guessing we might delete too much.
Etrecheck tells me that:
[failed] com.apple.midiserver.plist
[failed] com.apple.mrt.uiagent.plist
I would not worry about mrt.uiagent.plist. This is a new Mt. Lion addition to check for maware. But the midiserver should launch without problems.
So I think you really need to get rid of the digidesign stuff and to reinstall the system. Contact the manufacturer for help.
http://www.thexlab.com/faqs/uninstallingapps.html
Regards
Léonie