Perhaps, directly importing files from the network may have an impact. Importing local files from your computer HD is always preferred. However storing the Gerber/Drills on your network as a zipped file should eliminate any possible latency on the network.
Note: To test if network latency is a problem, try first copying a set of Gerber files from your Network onto your local computer HD. Then import those local files into FAB 3000. If there is a significant different in speed - compared to directly importing from the network - then you know the cause. If this does occur let us know, and again we do recommend zipping files on the network.