Object reference not set to an instance error when opening a hierarchy.

This happens if you have included custom properties in hierarchy property "user display property" and one/many of these properties were deleted. Just update this property value and remove any properties that were deleted.

Script Formula to find distict values from all the children of a node.

/*
This formula tries to find list of all the distinct property values for all the children of a parent node.
it helps to identify nodes that have different children with different property values.
*/

var cprt;
var childEnumerator = node.GetChildEnumerator();
while(childEnumerator.MoveNext()) {
    var propValue = childEnumerator.GetCurrent().PropValue("Custom.CPRTSchedule");
       if(cprt == null)
           cprt=propValue;
   
var re=new RegExp(propValue);
    if( re.test(cprt)==false)
         cprt=cprt+","+propValue;
   
}
if(!cprt)
    return(node.PropValue("Custom.CPRTSchedule"));
return cprt;

There are currently no applications available for login DRM Webclient cannot connect to application.

Had tough time isloating the issue and resolving it. we were getting this error inspite of drm services and engines up and running. no issues with IIS, Database, DRM, windows etc but still drm web client would not connect.

At last was able to get it up and running with the below changes. I dont say this is the fix for the issue, but it might help if you are facing a similar problem.

1.  Start IIS Manager
2. 
3. Goto IIS->Application Pool->drm_pool
4. Click Advanced properties and Click on Identity under Process Model section.
5. 
6. Change the Built-in account from NetworkSerivce to LocalSystem. Click OK and go back to main interface (Application Pool)
7. Recycle Application Pool (Click the recycly button on the right)
8. Restart DRM Application. Now test if it works.

If above did not resolve then try these

1. Create a new windows user. e.g. DRM_ADMIN (local system )
2. add the user to Administrator group.
3. click 

Security Policy - DRM WebServices

Tip: Everytime you make a change to security policy, make sure you restart shared services. preferabally restart both shared services and web logic.

I learnt it the hard way! :-)