I found another solution that prevents the repeating issue that Yuval was seeing. You need to check the "Perform Grouping on Server" in the Database Expert, Database Options, Advanced Options section. I was getting my data from a fairly complex stored procedure, it returned a very nice and clean table in SQL Query Analyzer, but Crystal was doing some very strange stuff and seemed to be rerunning the SP for each record it returned. It produced an exponential growth of records for each record I referenced in my report.

Just for Google searches to hit on this post. My Google query was Crystal Reports Details section repeating. Took a while to get to this forum eventually. I hope this helps other banging their heads with this issue.