yesterday, i downloaded the new version 6.1.1.
As soon as i started using Calc , i tried to use the “format cells” feature and the program crashed immediately. I rolled back to previous versions, and now i get the same problem permanently.
I am using a Windows 7 pro system.
Appreciate any help!

Why are you screaming? Which OS?

How did you “roll back”? As a rule you cannot install an older version correctly without previously uninstalling the newer one completely.
Did you Help > Restart in Safe Mode... (the LibO, not the System!)?
LibbO V6 claims to support Win 7 (as the minimum Version), but it may expect an update of Win 7 you didn’t. SP1 is explicitly required.

I’m using Win7 + LibO and it works perfectly.

You downloaded the installer from the official website:

Same issue, in diferent versions…