T,
Are you saving to own harddisks or to a common server or something?
It is always recommended here to open/save from/to own hard disk, and to copy from/to networks and removable media. You may be lucky (for a while), but the chances of file corruption and other unpleasantnesses are immensely greater when you use anything but the harddisk, and it is better to be safe than sorry.
In addition to the (far greater) risk of file corruption, some issues are mentioned here:
http://helpx.adobe.com/illustrator/kb/illustrator-support-networks-removable-media.html