I came across this one recently and found it was a pretty simple fix so I thought I should share it as it’s one of things that would annoy you otherwise.

I’ve been working with Microsoft Systems Center Operations Manager 2007 R2 to replace our existing monitoring system and I haven’t touched it for a weeks due to other work. When I came to view the Active Alerts I received the following message upon selecting some alerts:

An object of type MonitoringAlert with id xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx was not found

When you access the SCOM/OpsMgr console, you cache the alerts in your profile in a file called momcache.mdb. This error relates to this cache file – the fix is to clear it.

There are 2 ways to do this:

1. Start the OpsMgr console with the /clearcache switch.
   

    “C:Program FilesSystem Center Operations Manager 2007Microsoft.MOM.UI.Console.exe” /clearcache

2. Simply delete the momcache.mdb file which can be found in the following location:
   

   Windows 7/Vista, Server 2008/R2

   C:Users%username%AppDataLocalMicrosoftMicrosoft.Mom.UI.Console

   Windows XP, Server 2003

   C:Documents and Settings%username%Local SettingsApplication DataMicrosoftMicrosoft.Mom.UI.Console

This should sort your problem.