Performance slow on network

We retrieve our files from a network. All our files reside on servers approx. 1 mile away from the pc's. We have experienced very slow open and save times even though we are using a T1 connection. The problem lies after we have opened the part or assembly. It seems as if everything is rotating in SLOW motion. It takes much longer to even rotate the object. This is happens on a regular basis. This will happen on all the machines at different times. Most of the time it works just fine. Very frustrating when trying to get a job done. Sometimes we will reboot our pc's but that does not always work. Can anyone explain to me why this happens? What can we do besides getting a local server? Thanks for the help