MS Windows Server 2003 incorrectly reporting out of disk space?

Random users, trying to save random Excel files sometimes (not always) receive an out of disk space message when trying to save their Excel files across a network onto a MS Windows Server 2003 server. The server has approx. 200GB of free hard drive space. One thought was file size. One file is 5.9MB and another is 12+ MB. Another thought was the network, but nothing has changed here. What has changed was that these users received a new File\Print server several months ago and this problem has been intermittent. The software load is the same for every server and the hardware is consistent. Windows Update has been run on this server. Thanks!