Attribute history report error logs

I would like to know, where the log files related to Reports. When i run Attribute history report some time i get an error message and some time i get only Introductory life cycle phase details in the report. I could find some inforlation like these kind of issues happens, when there is a special characters. If some one can help, how to find the exact special character or the related log file it will be useful for me.

Thanks, Suneel