There are some quirks when converting to a newer version for some types of database connections. We ran into problems with our reports with Oracle connections because we'd edited the SQL to remove the table owner (which is different for each of our environments.)
Here's what I would try:
1. After opening the older version of the report in the newer version of Crystal, do a "Set Location" on the report. Save and try running.
2. If that doesn't work, you may have to recreate the report from scratch (this is what we had to do...) However, this is not as bad as it may seem because you can have both versions open and copy/paste objects from the old report into the new one - this is the easy way to get all of your formulas into the new report without having to open the formula editor to retype them.
-Dell