Cubase 7.0.3 has been a complete Crash-Fest. After loading a backup the file is either corrupt or Cubase 7 says it has been made with Cubase 1.x!! See Screenshot…
OSX 10.8.3/10.8.4 C7 7.0.3 64bit
I want my Atari back!
Check and make sure that your old pref file from early cubase version which is sat in the appdata folder is not still there if it is that will be your major problem delete it or copy it to your desktop then delete C7s pref file reload C7 it will find all your plugins again and you should have no more issues loading up early versions of cubase tracks. I had the same problem and now it’s totally fixed and works perfect.
Hope this helps
I’m not trying to open up an old projects. This happens after a crash and a backup is loaded saved with 7.0.3.
It doesn’t matter. The prefs file from an earlier version could be the cause of your crashes to begin with. Try it, what have you got to lose? 
True, even if you fully restore, you can be restoring the old preferences …it only takes a few seconds and the new file may make the difference you need
The .BAK cubase backup file is corrupt because cubase crashes on saving. Once that happens there is no way to open a corrupted .BAK file. No diddling with the pref files will help the situation, according to the support folks at yamaha.