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.

I, too, have sprint, use lg musiq. (I do not recommend this phone). Data port and AC charging port are the same, meaning that as usb connection , your good as long as battery holds out. (abt 2-3 hrs). Then you have to go offline to charge phone.

Have tried bluetooth. here is what I found after 6 months of f***ing around: could not pair w/toshiba-intel setup; moved to hp dongle and broadcom(widcom) stack - that setup was as solid as an agoraphobic stuck in a walmart cashier line - have changed to iogear dongle w/broadcom stack. Works like a charm, bt connection, though slow, is solid, w/very few discos.

lately have had same connection problems as others here.

cannot use port 6347 - port is unavaliable ???
have a firewall signal on tray, came out of nowhere.

also use peer guardian2, (forever), and looking at reports, shows blocks on "limewire" at addresses such as 70.5.224.106
99.201.80.14
68.246.97.127
among others. What is that about?? Never before have I seen this....

oh... latest versions of everything... xp pro sp3, limewire xxx-8 pro, java 1.6.10 (no issues b4), asus laptop, centrino dual, 3g ram, etc.

anybody find anything out?

I have a feeling since the courts wanted Verizon to give up info on customers downloading, that the ISP's figure it is easier to **** us off then it is the have the government mad at them