I'm curious about how you managed to store symbology in a geodatabase because there is an ArcGIS Idea, not yet implemented, to do just that.
I suspect that you may just mean that when you add your 9.3 layer file to ArcMap 10 it can no longer locate its ArcSDE 9.3 feature class.
If that is the case you should be able to go to the Source tab of the layer properties, change it to the ArcSDE 10 feature class and then Save As Layer File.
If you have lots of layers to reset data sources on from one ArcSDE instance to another then check out Repairing broken data links.
Alternatively, and I've not tried it, but the Add Representation tool seems to accept a layer file as an import_rule_layer.