I can't think of anything. Has this always been the case? If not, you might try a verify database and see if that works (it should). The next thing that I would try is to change the name of the alias, and see if that helps. If you have multiple databases, I would also check that your ODBC connection is pointing to the correct database. I don't know how many times I have changed something in one database, only to find that my report is looking in another.
I am all for doing just about everything on the DB server, which is probably a 'faster' machine, and the software is optimized to handle the data as group. Let the DB software do what it is best at, and let Crystal handle the formatting (what it's best at).