I use a MotoRAZR V3m Cellphone as my modem and Sprint as my ISP. The phone's display and the PC software interface had indicators for my connection state.
Problem:
The phone would go offline yet the PC stayed online?!? I made the error of clicking the stop button and restarting the PC software, upon which time I received a "No Modem Device Installed!".???
Nothing worked: system restart, software remove/re-install, System Restore...
I eventually re-installed the entire OS and softwares. That worked. I got hit twice more before stumbling on an answer. First...,
When the phone goes offline and the PC doesn't, I unplugged the phone from the USB and wait for the disconnect sounds + 3 secs. And I wait for the software to detect the missing device. Then I plug the phone in and the software re-intializes automatically. I usually have to do this once per internet logon session.
Second...,
A tip from the forum; I connect manually in Limewire after it finishes loading.
And something I discovered; Most ISP's look for a browser signature. I open IExplorer goto Google, minimize it, and then continue w/ Limewire.