We've recently started getting an error in the application log of microsoft exchange server 2007 with the following description:
Event ID: 9667
Failed to create a new named property for database, "First Storage Group Mailbox Database" because the number of named properties reached the quota limit 
User attempting to create the named property "NETWORK SERVICE"
Named property GUID: 00020386-0000-0000-c000-00000000000046
Named property name/id "x-jxp"
Can't seem to find a cause for this - nothing on Internet searches