Not Supported -- Err msg coming in Crystal Report

[manush]

Hi,
I wrote a pl/sql package and connected it to crystal report to access the oracle database and it worked fine. Then I changed the package where I used a string variable to write SQL and then used DBMS.SQL package to execute the same sQL. My package compiled well but when I tried to preview the output from the crystal report, it is giving "Not supported" error msg.
Pls suggest a solution.

Manoj