The other day I needed to add a large amount of objects (860) to an availability report. After the report ran I noticed that only 500 objects were present in the report view, as it turns out this is by design.
In your registry you need to browse to the following key:
Location: HKEY_CURRENT_USER\Software\Microsoft\Microsoft Operations Manager\3.0\Console
Create a new DWORD value key that is named MaximumSearchItemLimit, and then assign it a decimal value to reflect the number of objects that you want to display. For example, use a value of 1000 if you want to limit the maximum number of objects to 1000 instead of the default of 500.
Value: 0 to 65535
Close and re-open your console.
You will now be able to search the number of objects that you set the value to.
Note: This needs to be applied on each machine running a console that you want to remove the restriction from.