McAfee is much the same way.. It generally won't install while Ad-Aware is on the machine.. It's important to note that best practice indicates there should only be one real-time antivirus and one real-time antispyware running on a computer. Ad-Aware installs its own "Service" and is therefore running in the background causing issues with other such antispyware programs also running in the background.. Using more than one such real-time scanner cause problems and as such, Norton is telling you the current situation must change..
It's your choice where to proceed from here.
Hope this helps.
Can these two programs co-exist? I installed the adaware and pc would not reboot without opting for last good congig. i uninstalled the adaware. now back to normal.