execution time of a report

[a.info]

Hi all,

I have a report with a prompt time.
when I run the report on a period example January 2013, I get the result in a few minutes. but that launches in March 2013, the report runs without result.

I have the SQL query generated in the report and I run directly on the database and I got the result in 2 minutes.

normally the difference between the two lines retoiurnées periods is 30 lines.

Do you have any idea please?

Thank you in advance.