As I said, you could try repairing the Office installation. It won't do any harm. If that doesn't resolve things, it's likely your problem file has content that Office legitimately warns you about (e.g. macros). Saving the file in the xlsx/xlsm format (as applicable) might resolve matters, as might changing one of Excel's Trust-Centre settings.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]