I can't open .xls I created with 4.2.5 files with 4.2.6

After creating several .xls files in Calc yesterday on 4.2.5 using Windows 7, I updated to 4.2.6. Now I get an internal read error. Internal Import error. What can I do to correct? Other .xls files in the same folder are okay. Is anyone else having a similar problem?

I reloaded vs 4.2.5 and can read files. ???