Slow Generation of Report
do you query on Events directly, if so, what timeframe do you use?
In general for timespans longer than a day it is probably the best if you set up trends for it.
When the reports go off the grid check to see if they show up under the archive tab. I've had occasions where the report will generate (slowly) and never present but the report will be archived correctly.
Also when building your query ensure you are using indexed fields.