I was advised to select Compatibility View in IE8 (via Tools) and this has allowed me to edit the settings on a new policy. I won't be able to test the new policy until next week but at least we've made progress.
as long as you allow the local versions of the VSE 8.5 to add their own exclusions, and not have them over-written by the default group policy, you should be ok.
for my setup, i just unlock the console on the system with the admin pwd (we lock everything down to stop user tampering), then open the On-Access Scanner and click on All Processes and the Detection tab. At the foot of the window is the exclusion button, and there you can specify the the folder (and sub-folders) of the Sage software package.
i don't have ePO 4.0, i know my system does not allow individual policies, its groups only, so if only one machine needs the exclusion, its a 5 minute job.