Opmanage instability

Hi

Over the past few months, Opmanager has been getting a bit unstable. Things like

* HTTP 500 errors when trying to log in
* Login screen presented but cannot log in, browser hangs
* Viewing some interfaces or adding new devices hangs browser
* Alarms not clearing, resulting in phantom 100% downtime

OpManager is managing about 150-200 devices, on a P4-2.4ghz with 512mb ram.

Can you please advise on ways to stalblise the product?
Thanks
David