Chuck,
You didn't mention was the data source type of your Report Caster repository is and that will affect the answer.
If your repository is an RDBMS like SQL Server for instance (ours is DB2), there is an auto log purge function that runs every day to delete log records prior to a certain date. The default is 30 days. If you log onto RC using an admin id, go to Schedule Log and then System, you will see a schedule called SYSP0000. This is the auto log purge schedule. You can look at the log reports for it to see if it is running or not. Again it may be that there is something wrong with the data base.
If your repository is a set of FOCUS files, then you will have to do REBUILDs with a purge date on a scheduled basis. I haven't done this in awhile. I would suggest that you check out the rcadmin.pdf manual for details.
Remember there are two log files, BOTLOG and BOTLOG2, the latter being much larger as it holds the detail lines.
Ginny
---------------------------------
Prod: WF 7.7.01 Dev: WF 7.6.9-11
Admin, MRE,self-service; adapters: Teradata, DB2, Oracle, SQL Server, Essbase, ESRI, FlexEnable, Google