RSLogix500 "unexpected file format"

I am trying to open a file (.RSS) in RSLogix500 application offline and am getting "unexpected file format".
I can open other files with the same RSLogix500 application without problems and I can take the same file (.RSS) to another PC that has RSLogix500 application and open the without problems.
Any ideas?

Probably a version conflict. Files created with a newer version of the software sometimes will not work with older version software. It also might be a bad or corrupted "save". Try to find an earlier .bak file of the same name to see if that could be the problem.

version

Thanks.
The Version that is working is 5.20.00; the Version that has the problem is 2.57.00. I tryed to open the file from two different saved dates and had the same problem.

Definatly a version problem. I had a similar problem today. The file was saved in V7.10 and i had v7.00. I could open the file but when i tried to go online if said it was corupt. Most of the time you will find that if you can't open it or if you try to go online and can't but LINX sees it, then it's a version problem.