If after you copy the file it runs without a problem, then the problem is in the network.
It might be one of the following:
1. Slow network, Make sure you use full duplex 100MBPS network cards AND that you hub supports 100mbps, if there is only even one node that is only 10mbps then the only way for the other nodes to utilize 100mbps is with a switch.
2. Unreliable network, make sure you use CAT 5 cables, the cables are not too long, the are wired correctly, they are crimped correctly, the run is not to close to any electrical wirings or device.
3. the folder has too many objects and it takes a long time to display the contents. Which make you think that it is freezing up.
4. Also make sure that in any other areas in the network the computer performs fine.