Crystal Report 8.5 showing without data after cetrain time

Hi to all!
this is my first post on this forum.

I have vb6 application with crystal report 8.5 , we have craxdrt and crviewer to show the crystal report on application. While after pass the parameter the report works well. After some time pass the same parameter the report doesn't show any data.

After close the whole application then try to open the report it works fine. So what is the error.

thanks in advance!