My Autodesk Inventor Professional 2014 (witch I downloaded as beta) can not now open it's own files, but it opens other models that I did using 2013, attached is the message that shows up, please clarify.
Some of the 2014 beta builds (including suites which included Inventor), were indeed out of sync in some of their database schemas despite the build numbering. You should be able to open the file in the final release version which is build 170.
I suspect you installed Inventor Beta2 & then installed one of the suites which included Inventor build 125, which did have an outdated shema. If you need to open this file in a beta build then you should install the Beta3d build or the final release.