Hope this link help you
"Native Inventor files are not backward compatible. The only way to open IV2012 files in a IV2011 system is to export the IV2012 files to a neutral format and import them into IV2011. This will lose all model feature tree history. "
But in AI 2015 running in win7 ultimate 64bit is working pretty well. No rse error, even opening different file, solidworks, autocad, etc. Is opening properly. Except if the version of files are updated. Like files at SW2015, I cant open or import, by the way . I use the computer from a friend. Which is more powerful than what i have.