There are a lot of issues that shouldn't be. You might try starting at new report. If you still don't get the correct fields to display in the database expert, you might want to reinstall Crystal. If other reports work fine, maybe it is just this file.
I have been writing reports with Crystal from version 7, and haven't seen what you reported...so I am thinking it is local to your copy...either the report is corrupted or the installation
Perhaps someone else has another solution, but I would at the very least try a new report and set the datatables up. If all looks ok there, I would continue with formatting the new report. The formulas you can cut and paste between...shouldn't be too bad, if that is the issue.