This is all Excel 2003 specifications and limits.

Reinstall Office is an ill-advice and that won't fix the problem. The problem is in that particular workbook, no problem with other workbooks.

Beside touching Excel limitations, usually a workbook with code may contains a lot of garbage particularly with large file after multiple modifying and compiling.

You should try "Clean-up" the workbook. Within Office suit, Access has a command line option to "Decompile" the file but that is not available for Excel.
You can find the code to help you to do so (I am intending to write an Add-in for this) or you can do it manually like this:

  1. Copy the problem workbook, called BookA, to BookB.
  2. Open both BookA and BookB in the same instant of Excel.

    In VBA Project box:
  3. Remove all forms, modules and class modules from BookA.
  4. Delete all codes in Sheet modules and ThisWorkbook module.
  5. Compile BookA

    Now, BookA is clean, it has no code al all.
  6. Drag ALL forms, modules and class modules from BookB to BookA.
  7. Copy all codes in Sheet modules and ThisWorkbook module from BookB to BookA with matching modules.
  8. Close BookB without Save.
  9. Compile BookA again.
  10. Save BookA.

You can compare the file sizes of BookA and BookB now to see how much different.