You are probably running into one of the (many) issues with the Excel export from Crystal. I don't guarantee this will work, but you could try this:
1. In the subreport, suppress every section except the one that your data is in.
2. In the main report, line up the top of the subreport to the top of the field next to it.
3. Make the subreport the same height as the field next to it.
Try the export again. If this doesn't work, there's no way to get around the issue.
-Dell