Only 1 instrument track works after a save

I am using Cubase 7.5 and use several instrument tracks per project. When I was on version 7.0, I was able to create several instrument tracks using HSSE (e.g. guitar, bass, piano) without issue. Now when I save/close cubase only 1 instrument track will play when I reopen the project. It’s as if the track is muted, but it isn’t. I can move the midi information from non-working tracks to the ‘working’ track and it plays fine. I can also create new instrument tracks, move the midi information, and it plays fine–until I save the project and close it. When I reopen it, I am in the same boat. So what am I missing? I can open 7.0 projects that have multiple tracks with no issue. I’m sure I’ve missed something here. Thanks for your help!