Having the same problem here. I tried several different work-arounds, including using the Select Data tool. Eventually I settled for running the Create Geometric Network tool in Batch mode.
Here is a related post: How to execute my model complete with one run? Geometric Network does not work correctly.
When Model Builder validation hangs me up like this, I've found the easiest work around is to run the tool inside a Calculate Value tool to get around Model Builder's validation preconditions.
The basic procedure is to create a Python function that runs the tool and returns the output, assigning the output to the data type the tool creates.