We use Grid Control 10.2.0.4, with a catalog repository database also at 10.2.0.4. It seems that after a week or two of being up, the response time of the web interface gets very poor (20+ seconds to navigate to a new page, when normally 2-3 seconds is seen). The only thing we've found to overcome it is a restart of the catalog database and the GC/OMS. No errors reported in the alert log, just unbearable slowness. Are there any Oracle DBA's using GC out there who have seen this (and hopefully found a solution)?
We migrated to the same version you are on about a month ago and have not experienced the problems you are. At least not yet. Have you checked the OMS logs? Is there excessive CPU usage and/or disk usage?
It appears that the problem is a symptom of a larger issue with the OMS. The direct cause seems to be that the OMS_HOME/sysman/recv/clob directory contained nearly 100K files. Why that is happening is the subject of an open SR with Oracle. Under Oracle's direction, I deleted nearly everything in that directory, and the performance has improved significantly.
Update, 1/15/2009: Oracle has opened a bug report for this issue. Anyone on a windows platform running GC 10.2.0.4 should keep an eye on this directory and periodically clear it out if it's not happening automatically.