Try the following steps until issue is resolved:
  1. If using multiple Details section with fields in each one, move the fields from one section into the other (place one field on top of the other)
  2. Delete the extra Details section and conditionally suppress the fields (rather than suppressing the sections)
  3. Right click on the Report Header section and select Section Expert
  4. Unmark Free-Form Placement checkbox
  5. Mark Suppress Blank Section
  6. Repeat steps 4 and 5 for each section in the report
  7. Click OK
Also, try suppressing other blank sections (Report Header or Report Footer sections).

If your report in Crystal has a subreport move the fields out of the subreport into the main report if possible (replacing the subreport).

Please review the Knowledgebase Solution BB722881 for Best practices for creating a Crystal Report for export into Excel.