Groupings on Crystal Reports...speed up...

Question

I currently have 3 groupings on my Crystal report and I am using stored procedure in SQL 2005 database. When I ran my report on my Web Application, it takes time to run the report ...takes around more than 5 minutes to run after I click on the 3rd group(in the group tree view)....I already enabled the "Groupings On Server" Option on the Crystal Reports but still takes time to run....Any ideas how can I make it faster??..Thanks guys.....