This occasionally happens in versions starting from 1.8.0 if the corresponding posts have not been properly migrated. Please go to the Tag Groups Premium settings and there to the "Support" tab. Under "Troubleshooting" press the "Migrate" button and then the "Purge Cache" button and check if that helps.
If you are using a plugin or service for caching, purge that cache too.
In some rare cases other plugins or themes may interfere. In that case you can turn off this feature in the tag clouds by adding one more parameter to all tag cloud shortcodes:
You also need to purge the cache afterwards.