Hi geogeek14,
When working with either an SDE geodatabase or a file geodatabase, ListDatasets("*","ALL") returned all the Feature Datasets in the geodatabase when run in the Python Window, from the command prompt (using the code snippet from posting #4), or from the command prompt inside Python. I tested the ListDatasets() function, and reproduced an empty list only if the geodatabase had no Feature Datasets. Does your geodatabase contain any Feature Dataset objects?
In order to get the Feature Classes within each Feature Dataset, ListFeatureClasses("*","","<Feature Dataset Name>") returned the feature classes. ListFeatureClasses() should return any stand-alone geodatabase feature classes if no Feature Dataset is specified.
In post #3 I'm seeing the results of ListDatasets() questioned, and in post #5 I'm seeing the results of ListFeatureClasses() quesitioned. If you're getting an empty list with ListDatasets(), it could be that there are no Feature Datasets within the geodatabase. If you're getting an empty list with ListFeatureClasses() in a geodatabase with known feature classes, there's more troubleshooting to look into. Let me know if you're seeing that.
John