Workbook Corrupted

Hi SDNers,

I have a workbook with multiple worksheets, and input query in it.

I have planning functions on it too. The workbook was working fine, and suddenly none of these workbook work. Am not able to perform a minor save function even. Looks like the workbook is corrupted.

Could anyone help me with the reason for the workbook corruption, so that we fix it, and such situations does not re-occur anymore. Thanks.