Used Range Won't Reset At All

I've tried everything, and still the UsedRange of our 74-row worksheet insists on running until row 1048576 (in an XLSM workbook).

Things I've tried:

• Delete unused rows
• Clear All on unused rows
• Apply cell style Normal to unused rows
• Check all formulas for references to entire rows
• Check all conditional formattiong references to entire rows
• And, of course, Save, Close, ActiveSheet.UsedRange to reset the last cell

Whatever I do, whatever I try, the last cell remains in row 1048576. Saving to XLS and back to XLSM, and some additional unhiding and resetting, do fix the issue, but destroys the formulas and formatting in the worksheet.

I'm about to tell my user to copy-paste content and formatting to a new sheet and throw out this one.

But I want to know what's wrong, how we might fix it, and how we can avoid the issue in the future. Any additional ideas?

PS: Exporting and analyzing the XML for the sheet is not an option, because the sheet is so bloated the XML file is uneditable.

I'm afraid this doesn't help me, sintek (but thanks for the input). I've Clear All-ed and deleted the empty rows; so I am 100% certain there is no content or formatting of any kind left.

I'm afraid I can't. It's confidential. I'll see about stripping the confidential information and uploading one of the problematic worksheets only.