Unable to set hidden property of the Range class

Hi

There have been quite a few posts relating to this - but none has solved my problem.

I have some vb that hides rows in a report where it comes across an empty cell:

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I select a parameter from a dropdown and this updates the report. I then call the vb with Call HideRow(Worksheets("3.3").Range("c9.c68"))

Sometimes I get the message: Runtime error 1004: Unable to set hidden property of the Range class.

Its intermittant and I've been unable to identify a pattern.
There are no comments or objects on the sheet.

Thanks

Any merged cells on the sheet?