This issue is caused by a character limit imposed in Crystal Reports 8.5 for variable fields. Try each of the following to resolve the issue.
  1. Reduce the number of characters in the field being used in the export.
  2. Upgrade to Crystal XI as it does not have the 255 character limit.
  3. Truncate the string field prior to its use in a formula.
  4. Create a String Array to store the strings.