Why is Calc 4.3 corrupting my Excel spreadsheets?

I recently upgraded to 4.3 and used a spreadsheet like I always have for the past decade. Only now Calc is mangling the structure. When I finally figured out what was going one, I had lost days of work. I can’t upload an example because I don’t have enough points.

Please try now to upload the file.

Funny, I just saved a simple ODS as XLSX and XLS, but the XLS is kinda messed up. This better report this. LO 4.3.3.1 on 7 Ultimate x64. EDIT: Moving the cell cursor fixed most of it.