Lynksys and Ubuntu on my Dell; HELP!

Hi-

I have two computers that share a Lynksys Realtek/router using Ubuntu.  Yesterday, I could access all my files/documents, etc.  Today, I went to work and cannot!  The LAN is connected.  The router is working. The internet is working.  I have run many virus scans and there are not trojans or viruses.  The files and documents will not open and I get a path/access/contact your administrator error message.  To make matters worse,  when I check in My Network Places the Ubantu is no longer listed.  However, again, my LAN is 'connected' and 'enabled.'  Anyone have any ideas?