No Audio in groups bar VST instruments

Hi, I have a new Win 8 install with Pro 8.0.20 on it.
When I open any project that worked fine on my previous win 7 install I get no audio through my groups?
The audio in the tracks are playing fine if I route them direct to the master output, but when I route them to the busses, there is nothing on the meters our going to the master output.

The exception to this is an instance of SSD which is routed to groups for snares, kicks etc then to a drums group and then to the master output - this is working fine???

This proves (I assume my vst connections are set up correctly) but don’t get why the groups won’t play.

checked all my routing from tracks to groups and this is fine?

If I create a new group and assign an existing track no problem this works fine, if I assign an existing track to any of the drum groups again, this works fine…?

what the hell???