I was just having a rummage on the Microsoft Premier Support site when I noticed an update to Communicator Mobile that had been released just last week. The KB article that describes the update and allows you to download the updated MSI installer is 954767.
The reason for this update is to fix the following issues:
1. Communicator Mobile 2007 suppresses HTTPS certificate errors when it fetches the NOO icon for the federated contacts. KB 954768.
2. You cannot log on to Communicator Mobile 2007 in High security mode. KB 954769.