I've heard of this many times but this past fall is the first time someone showed me the file that is having this problem.  It was a file that had very few entries per year and the client was still using the 2009 version.  I reviewed the file and found in fact had the country code changed to indicate it was now from the Simply Accounting 2009 US version.

I did a data repair and put it back on the client's computer and it worked just fine.  Because you are using the current version of the program, Sage may correct it under a tech support subscription but I don't know what is covered so it may be extra.  If you can't get it sorted out, I can have a look at the file for you.  You can contact me through my forum profile.