Thanks for the link, I had seen that earlier. It discribes the "MediaResourceListExhausted" message but doesn't speak of the "NULL_LIST" Is the NULL_LIST some default list? I can't find any reference to it on Cisco.com or here.
The only way to find out what device(s) are having the problem is to enable Detailed CallManager traces. Once you see the error in the event log then someone can take a look at the traces, at the time of the error, to see the call flow and what devices were involved. It would be best to enable these traces on all nodes in the cluster.
If you just want to know what NULL_LIST is, then I would say it is something like the NONE partition incase of phones.
This error message talks about the resources of a transcoder getting exhausted, which is not in any list, but in the NULL_LIST. All devices are by default in this list, if they are not specifically put into any particular Media Resource Group and thereby in some Media Resource Group List.
You can also check the application log on the Callmanagers to check for errors. If you have any error messages regarding this, please let me know and then we can try to find out what is goin on. Did any of users complain about any calls getting dropped (outbound or inbound from the PSTN)?
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.