LAN Connection Disappears

I'm trying to help my mom solve a problem with her Latitude D610.  Recently, she started having issues connecting to the LAN at her work.  When i investigated, I found that the LAN Connection wasn't listed, and that the device wasn't shown in the Device Manager either.  Just randomly, out of the blue.

 

I downloaded the Broadcom driver from the Dell site and installed it, but it did not solve the problem.  I gave up, with the plan to contact Dell technical service, but then the next day when I sat down to do it, the device and connection was showing and working fine again.  ...two days later and its disappeared again!

 

Any suggestions??

Thanks in advance!!