this may be related to the issue you reported with the RTTA not acknowledging the alerts.
Again, I would suggest the upgrade to the latest 6.1.x as there will be many defects added.
For the Messages from McAfee not showing anything:
1) Are you using a proxy and are the proxy settings correctly configured?
2) Can you check on the mysql database that the scehduler IUS_MESSAGE_DOWNLOAD is Active with this command (it should return 'TRUE'):
mysql> select isActive from iv_schedulers where type='IUS_MESSAGE_DOWNLOAD';