I thought Cubase 6 was a separate installation. I must be wrong because it jacked up my Cubase 5 projects, even when loading them in cubase 5 they sound all wrong, the effects are messed up for one, my midi keyboard won’t play anything (but it plays the same project fine in cubase 6). I’m REALLY not pleased. It would help if I knew what files Cubase 6 jacked up so I could try to restore from a backup, I don’t want to wipe my entire system.
Did it jack up Projects that you hadn’t loaded into C6? That would be mysterious.
If you had loaded them into C6, then some C6 specific settings may be affecting projects subsequently loaded back into C5. Can you give more detail?
Yes, projects I hadn’t even loaded into C6. In fact I was just trying to use C5, and they were jacked up. I was using the REVerence reverb, and I guess they decided to dick around with that, I never could get it back to normal so I had to rework it. They probably messed around with the impulses assuming no one could possibly be impacted if they changed them.
I had about 15 different version saves of the same song, and all were messed up when loading back into C5, even though I hadn’t loaded them into C6. I’ll never dare again do one of their “free trials” or even upgrade if I want any hope of preserving my past works.
Doesn’t add up for me. I think you missed something simple and my guess is that the files and/or FX are retreivable. Everyone elses C6 seems to work fine and most of them, including me, still has C5 and older C5 projects all running as they should.
Plus if the trial version really did do that we’d see several thousand posts on the matter. However. There only appears to be you. Should tell us something.
Not sure if this is necessary, but you asked. Control Panel>Programs, select Cubase 6 and uninstall. 
Maybee you installed it over the old C5 directory, normally the installer makes a new directory “Cubase 6” and thus seperating C5 and C6 installations physically.
Uninstalling C6 then would also cripple your C5 installation.
If you have a second PC/MAC then just switch the usb dongle and do a fresh install of C5 and then test your old projects, i workable, re-install your orginal PC.