We'll need more info.
What Ubuntu are you using?
Have you recently changed your wifi security from WEP to WPA?
Please copy here the results of sudo lsusb
We did update the modem/router to an Actiontec/Quest pk5000 unit. We were able to get on-line with the dell system after the installation, until we shut down the computer for Tgiving weekend. No change on security. Is still wpa.
Not sure what "sudo isusb" is...sorry, not familiar with linux queries or language. When I tried entering on command line it asked for sudo password and I've never setup one.