We were told groupshield 6 was supported by EPO 3, so had to move to version 7. You can still manage 6 from your exchange server though. To move to 7 I'd remove GSE6 completely, there are instructions on how to do this (KB55780), then have a clean installation of GSE7, upgrading was more trouble than it was worth! GSE7 will let you import the config file from GSE6.
hope this helps