PROBLEM WITH EXCEL

Use Excel Repair Toolbox is efficient corrupt XLSX file repair software, suitable for all data recovery activities, applied to Microsoft Excel documents.

For more: https://www.xlsxrepairtoolbox.com/

Restart computer.
Save changes more frequently in Word/Excel.
Add more memory. (www.crucial.com)

Good luck!

have you tried to read in one file and write back in excel format only the non-blank rows?

Try:
XLSX Repair Kit. The latest corrupt XLSX file repair software featuring a powerful data recovery core and a convenient step-by-step wizard for extra convenience.
For more information: http://www.xlsx.repair/

If doesn't help look for the answer here:http://www.filerepairforum.com/forum/microsoft/microsoft-aa/excel/653-i-get-a-message-that-the-file-is-damaged-or-corrupted

Excel may have "Ignore other applications" selected. See THIS Microsoft Knowledgebase Article.

Try going to Excel Options; Advanced tab; and under the 'General' heading: uncheck the box that says: Ignore other Applications that use Dynamic Data Exchange (DDE).

1. Click the Microsoft Office Button , click Excel Options, and then click the Formulas category.
2. In the Calculation options section, select the Enable iterative calculation check box.
3. To set the maximum number of times that Excel will recalculate, type the number of iterations in the Maximum Iterations box. The higher the number of iterations, the more time that Excel needs to calculate a worksheet.
4. To set the maximum amount of change you will accept between calculation results, type the amount in the Maximum Change box. The smaller the number, the more accurate the result and the more time that Excel needs to calculate a worksheet.

Excel Password Remover 2008

Excel Password Remover
Instructions
FAQ
Disclaimer
Excel Password Remover PRO

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Recommended links:
Password recovery software (Word, Excel, Outlook, Exchange, Visual Basic modules, Access, Winzip, Lotus 1-2-3, Lotus Organizer, Lotus Wordpro, Backup, Project, FileMaker, Schedule+, Money, Paradox, Act!, Mail, Windows NT)
Instant password recovery (Instant online recovery service for password protected MS Word and Excel files. Free online preview of encrypted file content. )
Visual Basic Password (Instant recovery of VBA-passwords in Office programs)
Excel add-in decompiler (Converts Excel add-ins into normal workbooks)

Have you ever forgotten your Excel workbook or sheet password?
Here you can download a FREE Excel add-in that removes/cracks sheet and workbook password protection in Excel®.
NB! This program can't remove file protection, i.e. if you are unable to open the file, this program won't help you. You could try Excel Key to remove file protection. If you need to crack the VBA-password try this one.
This Excel add-in (password.xla) works fine in Excel 5.0 and above (including Excel 2000, XP and 2003).
This program will remove passwords of any length, also passwords containing special characters.
Download here: password

I would try uninstalling Excel and Word and reinstalling. Something seems corrupted.